one of the popular lowcost setups is the v-groove bearing #2-has a 3/8 center bore- with or without seals- and is used on .125 angle-iron rail. a break-in period is required but they are accurate and can handle high loads. the next upgrade would be to purchase the v-rail made for the bearings. higher loads/ commercial type use supported rail- but they are pricey. My next build is v-groove (22 total) with built in room for precision v-rail upgrade at a later date.