I have tried both reed blocks,my 06 cr125 has a rad valve,icat,stock pipe,pc reg. silencer, the silencer makes a tiny improvment,on a 04 there,s a big difference. The rad valve has much better throttle response, low to mid improvment is huge, threw the midrange there,s a little improvment, topend a tiny improvment. The 06 runs alot better with the r.v., with stock gearing and 170 lb plus rider, it pulls hard enough that I want to drop a sproket tooth, much leaner jetting required, the 05-07 is already very rich all stock. Pull the reeds on the r.v. and polish the inside smooth,before ya install it. I installed the vforce on my 04 cr125 when new, throttle response is better than stock, slight midrange and topend improvment, the icat made a bigger improvment in throttle response and midrange. If your cylinder is stock get the rad valve,with the low to mid boost, it,s impossible to ever fall off the pipe. If your cylinder is ported for mid to topend, the vforce, has good dyno #,s on the topend they say. With the radvalve you want to drop a tooth, from the added boost, less shifting, let the mid pull longer.With the vforce you don,t think about dropping a tooth, because the improvment is slight.