Basic 2-inch nylon rollers with a 4-inch stem, bag of 10. These are non-bearing rollers, meaning there's no ball bearing inside, the stem just rides on the nylon wheel. They're the cheapest option and work fine on lightweight residential doors that don't get opened more than a few times a day. The 7/16-inch diameter stem fits standard residential hinges. For 2-inch track only. If you just need rollers that are quiet and don't care about longevity, these do the job. But if the door is heavy or gets heavy use, step up to the 11 or 13 ball bearing version.