I've got a couple of the XTRA 4000's. I used them for barbelling (the kind where you stay awake) and they're bulletproof. I sent them off to Felindre for service a couple of years ago, and all they found to do was fit new drag washers. They've been mothballed for several years as I've gone over to pins for most of my barbelling and I'll probably sell them. I don't know if the spools fit the XTR models, but I can tell you, if ut's any help, these spools are 2" OD at the open end and 7/8" deep.