I just got my small 21 yesterday, and my thumb is sore too! Fingernail is worn out and I'm sooo satsfied. Been using mine all day in the lab opening heavy duty bags that LAN cables come it. The blade simply glides through it.
Congrats I hope you're ebjoying your new 21 as much as me!
Congrats I hope you're ebjoying your new 21 as much as me!