The UIAA equipment standard provides a baseline for equipment performance in a test lab under controlled conditions on new equipment. Although these test conditions are relevant to the conditions encountered climbing, conditions encountered at the crags and the condition of the equipment are equally important. This recommendation from the UIAA member federation The British Mountaineering Council (BMC) provides vital equipment information that is NOT explicitly addressed in the standard, particularly failure modes of the equipment and recommendations for the use, inspection, maintenance, and retirement of equipment.
Sigma K8G
Description
Versatile carabiner with gate-wire Twin-Gate system.
The Sigma is a D-shaped carabiner and sees its prevalent use on belays, at personal anchor systems, and it can be used also in the quickdraws to clip the rope when you want to guarantee the total non-opening of the carabiner itself under stress from a fall in a hard pitch and with long protections and high risk of falling. Opening by Twin-Gate wire-gate system, which does not require any additional maneuver (e.g. screwing), making it safer and faster than other systems. Furthermore, it allows to avoid accidental openings that can occur for example due to contact with the rock, due to incorrect passage of the rope due to involuntary hand pressure. Two openings also allow greater resistance than one. Finally, it maintains its functionality over time and does not fear the presence of dust, earth, ice like other systems. The gate-wire combination facilitates its use even with gloves, and allows you to easily attach all types of devices (brakes). Individually tested, with the date of testing and progressive number laser-marked on it.
Retail price
US$ 14.99
When you click a link below and then checkout online, no matter what you buy (climbing gear or not), we get a small commission that helps us keep this site up-to-date. Thanks!
Award Image
Weight (g) Weight (g)In grams, the weight, as stated by the manufacturer/brand. |
57 g |
ShapeShapeRule of thumbAlmost every carabiner you use will be non-locking offset D’s, with the exception of a Pear/HMS locker as your belay ‘biner. Offset D (aka Modified D)60% of the market 
A modification of the standard D shape, the top of an offset D is much wider, allowing for a larger (and superior) gate opening. When loaded, most of the weight is transferred to the spine of the carabiner making them stronger than most other shapes. Used for top and bottom quickdraws, as racking carabiners, and lightweight lockers. Pear / HMS22% of the market 
The Pear/HMS carabiner is used primarily for belaying and/or setting a powerpoint in an anchor. The wide top means they can hold a lot of gear. They are almost always locking and are generally heavier (than D/offset D's) because they need more material to gain back strength lost due to their shape. Oval8% of the market 
The first carabiner shape to be mass produced. When loaded, the pressure is shared equally on both sides of the ‘biner. Since the weaker gate shares the load with the spine, oval biners aren’t as strong as shapes that direct the load to the spine. The bonus is, your gear rests squarely in the middle, so it's great for holding nuts, pulleys, and prusiks. D (aka symmetric D)7% of the market 
D’s have a symmetrical shape that sets the rope closer to the spine, putting the load on the spine (versus sharing the load with the weaker gate side, like the oval). Since the strongest part of the carabiner carries the weight, D’s are the strongest shape. Downside: Smaller gate openings than the offset D. Quick Link (aka Oval link, Maillon Raptide)1% of the market 
Although most climbers wouldn’t refer to this shape as a “carabiner” they are certified by the same EN standard as all the other carabiners. These semi-permanent links ensure the gate will not accidentally open. They're used when setting up a semi-permanent rappel station (not used while climbing up). Semi-Circle / 3Dless than 1% of the market 
Semi-circle: Mostly used by Search and Rescue as this is a great way to secure a chest harness. Learn More
Pros and cons of each shape, graphs and more examples |
D / Offset D |
LockingLockingmain non-locking carabiners uses:
main locking carabiners uses:
screw gate vs auto-locking gateScrew gates are generally lighter and cheaper. Auto-locking gates are usually considered safer as they automatically snap shut, not counting on one's memory to close and are harder to accidentally unlock. The debate comes on opening speed as some are much faster while others can be a struggle. Learn More
See the newest auto-locking gate technologies |
Auto - 2 action |
Straight or BentStraight or BentIt's easier to see the difference between straight and bent gates on solid gate carabiners: 
Straight GateThe standard. Always used as the bolt-end of the quickdraw, and still sometimes used on the rope-side too. Also used for racking gear such as cam and nuts. Bent GateCreated to make it easier to put the rope into a quickdraw with their larger gate opening. Primarily used on the rope-end (bottom) of quickdraws. Extra Notes
Important NoteMany manufacturers are now making the bolt-end carabiner come standard in silver (to match the bolt color), and are coloring the rope-end with other anodizations. Do not mix (interchange) bolt-end carabiners and rope-end carabiners. This can be very dangerous as small abrasions made by the bolt can easily wear your rope. DMM put out a great video/write-up on this issue. |
Bent |
Full SizeFull SizeFull size carabiners are easier to hold but generally they're also heavier. This is a totally debatable field as there is no official size, weight, or gate opening necessary to be full size. There are no certifications and this isn't a standard the manufacturer's normally describe specifically. We did our best to compare (descriptions, in-person use, etc), as a way to help give more information about this carabiner. Like always, if you see something that seems totally off, send us a note. |
Yes |
KeylockKeylockA keylock nose means the nose is smooth. Keylock carabiners are also known as: snag-free, notch-less, and hook-less. 
Keylock BenefitThe lack of a hooked nose makes for less snagging on gear and bolts – a dramatic improvement. Keylock DrawbackGiven that they’re more complicated to manufacture, keylock designs often come at a higher price, especially in wiregates. Worth ConsideringThere are more design features necessary to guarantee a snag-free experience, like the curvature of the nose. Some keylock carabiners will still catch on the nose because of the lack of a smooth nose arc (smoother the arc, smoother the clip). Learn More
Check out our blogpost that goes over carabiner nose design to get all the details |
Yes |
Solid or WireSolid or Wire
Solid GatesGenerally on beefier carabiners, so they're usually heavier and more durable. They can also feel more substantial in your hands while clipping. Often favored by sport climbers. Wire GatesFeatured on the lightest carabiners, so they're favored by trad and alpine climbers. Some considerationsIf you want keylock nose carabiners, then solid gates will be much cheaper compared to wire gates. When wiregates first came out they were not trusted (too new, looked too simple). Now, it's proven that wiregates have less gate flutter and gate shutter than solid gates. Learn More
Compare gate flutter and gate shutter |
Solid |
Gate OpeningGate Opening (mm)Gate opening refers to the distance between a carabiner’s nose and the fully open gate. 
General Guidelinestop of your quickdraw: 17 mm – 22 mm Adding bias towards a larger gate opening is a great option once you’ve narrowed your choice to a few similar carabiners and need help determining which one is the best. Learn More
Gate opening comparisons, examples, averages, shape, sizes, graphs, and explanations |
23 mm |
Number of ColorsNumber of ColorsThe number of different colors that you can find this carabiner in. This color-coding practice was started with just 2 colors, usually silver (that goes on the bolt side of a quickdraw) and another color for the rope side. Now, carabiners come in 5+ colors sets known as "rack packs" so your carabiners can match your cams. Climbers can also match their carabiner color to their harness or other gear just for fun. Learn MoreCarabiner Rack Packs Explained |
1 |
Lock IndicatorVisual Warning
A lock indicator is a visual warning only seen on locking carabiners. It adds some sort of visual to show if the carabiner is unlocked such as the color red, a danger sign, an unlocked image, etc. When the carabiner is locked the visual indicator is hidden. Only a small list of manufacturers add this safety feature, although you can easily add one yourself with a permanent marker. |
No |
Strengths (kN)Strengths (kN)In kilonewtons, the strength, as stated by the manufacturer/brand. Major Axis Closed Gate Strength
This is the strongest orientation and the way carabiners are designed to be loaded. Major Axis Open Gate Strength
This strength is measured because while climbing, carabiners lying against the rock can be opened slightly as they move across an uneven surface. A carabiner can also open slightly during a fall as the ‘biner starts to vibrate, dispersing the energy (also called "gate flutter"). A weak gate closure (due to a poor/failing spring or an over-stressed wire) could also leave the gate ajar. Minor Axis Gate Strength
Carabiners are not intended to be loaded along the minor axis (cross-loaded), but it is possible for a carabiner to unintentionally rotate during use, especially while belaying. Of all accidental misuses of a carabiner, cross-loading is the most frequent suspect, which is why there is a rating for it. Generally wire gates are stronger than solid gates in the minor axis. During the test, the wire gate bends, absorbing some of the force, as compared to a less pliable solid gate. Learn More
How carabiners are rated, recommendations and strengths. |  30 kN  9 kN  9 kN |
No reviews yet.
I’ve seen a lot of online debate contesting the usefulness of this carabiner, the naysayers claiming it’s a “gimmick” and a “solution to a problem that doesn’t exist.” Many folks are excited about the new innovation albeit a little hesitant to commit.
I agree that this debate is most similar to the question of an ATC vs GriGri. Is it necessary that everybody change over their locking ‘biner fleet immediately? No. Do Twin Gates assist in reducing risk? Yes. Is it worth consideration when buying lockers in the future? Yes.
The Twin Gates are an interesting take on the locking biner concept. They work, and they work well. They can be finicky to operate, even for an experienced user, but by far their biggest downfall is their biggest upside: innovation. Someone who’s gotten used to the idea, or is curious about new gear, will learn to use them quickly and effectively. But pass them to your partner on a multi-pitch route and they look at them with distrust. It’s a great concept, it really is, but it will take a while for the general climbing population to become accustomed enough with the Twin Gate system for it to be widely adopted. For those willing to try something new, prepare to be questioned.
The combination of solid and wire gate was much easier to operate and after a short period of familiarisation became pretty much second nature. How much did I like this carabiner? Well I went out and purchased another two with my hard earned pennies and I’ll happily buy the Plume when it becomes available. In use it was quicker to set securely than a standard screw gate with no risk of forgetting to screw it up and there was never a risk of it freezing shut even when getting dripped on at a (semi)frozen, icy belay. Is it the perfect locking carabiner? Not quite. There is a familiarisation period or ‘learning curve’ before you feel totally happy with them and they are a little trickier to unhook from rear racking loops on your harness. There are some placements when it’s a bit trickier to ‘hook’ the outer gate than a standard carabiner, such as a deep set wire where the loop has dropped into the crack, but it’s not a deal breaker especially as I tended to use them mainly on the rope end of extenders/slings. Something I didn’t consider however is that you may be totally happy using your shiny new twin gates but your partner may not! After we swapped leads for the final pitch of Crest Route in SCNL I had to suppress my laughter as cries of ‘Witchcraft!’ assailed me from above as Bruce endeavoured to open a twin gate I’d passed to him on a long sling!
If you know of a good product video that should be here, let us know, and we'll put it up.
If you're looking for gear videos in general, check out our Vimeo and YouTube channels to see the newest gear.
A pictoral representation of UIAA-121 and EN-12275 standards for connectors (the UIAA's fancy word for carabiners).