Rich, I am still struggling with my kit. In looking for those 'sprocket rings' I tried to cut off plastic ones from Forces of Valor sprockets, (they measure about 0.200" smaller than Tamiya M26 ones, and just looked too small). I also tried to cut down some Tamiya M26 ones, (couldn't figure out how to clean up the remnant so that it looked good). I didn't have any spare Heng Long plastic ones to try out, so I decided to order two pairs of metal ones from Ludwig, at a cost of 10 Euros for the four of them. VERY disappointed in them, and posting this as a warning so that you don't throw away your money on them. They are cast in most of the circle of the sprocket, with a small part that is glued in to close the loop. Three of them were so out-of-round that they looked just plain silly, (1.585" one axis and 1.780" the other). Not sure how to straighten them out without breaking them. The fourth one needs to be re-glued at the small closure part. Some of the parts he offers on this kit (boom, resin storage lockers, front roller, and both towing devices,) are much easier than trying to scratchbuild them yourself, but these sprocket parts really fall down in quality. I will probably try and source a couple of plastic Heng Long sprockets, and try to cut them down for use. -Mike