Probably .36s, but it's best to get a couple different weights, from a couple different brands and go out and see which shoots the best for your specific rifle.
Also, I said be careful which cylinder set you purchase because CA does produce 2 different advanced cylinder kits, one of which is APS specific, one of which is M24 specific - the only differences is the length of the piece where the handle attaches. The shorter is for the M24, the longer for the APS. I say be careful because many sites advertise them as interchangeable, which they in reality are, the difference just determines which handle you need.