Two Capo Day! Muiti Finger Type Silver Capo Picks Tune Key Clamp for Acoustic Guitar #ORP $8.88CAD eBay
I think the design goal to make users twist their wrists trying to get it on guitar:)
Since this is a new-to-me design I have decided to call the design Spring Piston. There are two models, a single finger and a 3 finger one. The piston design is similar to finger exercisers from Planet Waves and other companies. In fact, you can use the 3 finger one for just that. It's tension is higher than the stiffiest setting on my PlanetWaves VariGrip Exerciser. Use it to improve your pinkie finger hammer-ons I found it almost impossible to get the single finger model off a hanging guitar. My finger was too weak and the angle was too awkward.
Looking at it's suitability to purpose. I have to say, once on the guitar, it works, but because of the stiffness of the piston spring, it may not be as quick change as you would like. It's large size and small back of neck pad makes is difficult to store on headstock when not in use.
Here we have it posed to compare size to a pack of strings and the smallest capo in my collection (a G7th) ..and my Varigrip, which I do not use as often as I need.
There is a good point! The mechanism of the piston is so far below the level of the fretboard that it does not interfere with my knukles or hand no matter how weird my hand is positioned. But for me this capo is too bulky for regular use. Certainly a conversation piece.