This track is designed to fit on standard 1/2" pitch bicycle chain - BMX or similar. The gap between the link holders is designed to allow a standard width skateboard wheel to run in it. Each track link is 24mm long and 100mm wide.If printing in ABS, keep the bed at 110 degrees C, head temp 240 degrees C, to minimise heat distortion. File is for single item, best to print in a block of 5. The design already includes a raft. Don't specify support structure, it's not needed. I've not tried it in PLA yet! Degrease bicycle chain, then dismantle it with a link pin remover. Yes, it's time consuming, and you may wear out one or two tools if doing a big track! Put the pins to one side, they aren't needed for this build. You will replace them with M3.5 x 30mm panhead bolts. For example, if making a chassis approximately 22" long as I am doing, you will need 4 bicycle chains, 100 of these printed links, 400 bolts and 400 nuts, 8 skateboard wheels and 8 sprockets. Printing may take a while, it took me nearly 2 weeks, doing 10 a day, with a few wrecks. To assemble, put 2 outer chainplates(flat) into recesses inside lugs of printed track part, put a bolt through one of the holes to keep them in place and aligned. Holes may need cleaning out with M3.5 drill to allow bolt to pass freely. Then take 2 inner chainplates(dimpled) and 2 rollers and sandwich the rollers between the plates. The dimples will hold them in place. Hold the outer chainplates apart, non-magnetised tweezers are usefil for this, and slide the inner link into place, it should just fit - secure with a bolt and M3.5 plain nut. You could use M3.5 nylocs, but they cost a fortune for some reason! It's cheaper to just use plain nuts and secure them with a blob of paint on final assembly.