i havent had any trouble, it is the same part number for both the x3 and the defender (hd10 at least) make it easy for me to inventory belts per the schematics from BRP. I have a couple new spares and a couple old for each. i carry 1 extra on each machine and can swap as needed. I run OEM belts and keep a WBB on the x3 as it was a decent one for the price as a spare.
steve