I think someone on here explained this in the past. This is what I wrote down so I could remember it, I hope it works for you:
To Remove Thunder 9 UC-Pro Grips: With the hammer down, push a small screwdriver into the small cam at the bottom of the grips. (it is not really a screw, it merely turns to lock/unlock the grips)
Holding the cam in, gently turn it to the right about 1/8" to lock it in place.
Reach fingers up into grip frame and 'gently' pry outwards on the grips to remove them from the frame.
NOTE: It can be tricky to get the cam to pop back out correctly when you reinstall the grips.
To Remove Thunder 9 UC-Pro Grips: With the hammer down, push a small screwdriver into the small cam at the bottom of the grips. (it is not really a screw, it merely turns to lock/unlock the grips)
Holding the cam in, gently turn it to the right about 1/8" to lock it in place.
Reach fingers up into grip frame and 'gently' pry outwards on the grips to remove them from the frame.
NOTE: It can be tricky to get the cam to pop back out correctly when you reinstall the grips.