I bought 2 of these mini biners to try as a summer/rock alpine draw. First off, "mini" is no exaggeration!! If you've ever used the Camp Nano 23 and thought it was too small, then don't even consider this biner: its even smaller!
The Metolius Mini biners are priced to be good value compared to the similar Camp Nano. The Mini has a moderately stiff gate and very small gate opening. (Note: for reference, I wear a men's size large glove/mitt and with a bare hand could not fit an index finger in the gate opening - this makes clipping difficult. Alternatively, pinch-clipping is equally difficult because the biner is so small that there is little to hold.) Hence, these biners are too small for alpine draws, but work well for my alpine umbilicals where they won't get in the way or flip around like the Nano's.
Overall, the biners are good value in the "ultralight" category, but if you want "everyday lightweight" alpine draws then I'd recommend the Nano's or a larger lightweight biner. For example, a personal favourite (and highly recommended) in the "light full-size biner" category is the DMM Shield notchless biners (35g) or Wild Country Helium (33g).