If your rifle is an RC, it could be ANYTHING, as RC stocks don't match the rifles.
Best way to check - move the rear band forward (after removing the band spring of course!) If you see a small rounded end rectangular nut exposed under the band in the wood, it's 10". If you don't, it's 12"
There is another thread on this subject but it's important to measure in case the stock has been changed. Just
insert a stiff piece of wire and mark it where it meets the half way point of the front sight. This will tell you if it
takes a 10 or a 12 inch rod.