The rubber is very stiff and it is dead flat

The hard rubber contact surface material is firm enough, yet malleable enough to conform to the strings.

I also worried about the super hard plasticky rubber causing undue damage to the finish on my neck

this is a great capo, really firm and good quality with a metal frame and thick durable rubber

The rubber is also very stiff (harder than car tire rubber... think more like dried-out pencil eraser).Pros:Construction is solidSpring is strongCons:Rotation action isn't very smoothFlat (for my guitars anyway)Cheap

Capo doesn't have enough pressure, it either mutes or rattles high and low E

Tested on 2 acoustic guitars and 2 electrics and the top and bottom E strings were never held down

Doesn't clamp the low E string very well on higher frets.

Either my low E is a dud or