Stem length variety stocked
We carry both 10-ball sealed steel rollers and nylon rollers with sealed bearings, plus the short stem and long stem versions, because houses in this area were built across a wide enough span that stem length isn't a safe guess. We don't carry every bracket variation for every door brand ever sold here, and if your track hardware is a less common setup, that sometimes means a short return trip rather than a one-stop fix.
