Our truck carries the torsion springs, cables, and rollers that cover most of what's out there today, plus the common opener models. Where Glen Ellyn gets specific is the 1972 housing stock: openings built to that era's standard width sometimes take a spring size that newer production doesn't use much anymore, since door manufacturers shifted standard thicknesses and weights more than once since then. If your opening is original and hasn't been re-trimmed, we can usually match it from stock. If it's been modified somewhere along the way - a wider header cut in, a different track mounted - we'll know on the measurement visit and order ahead of the install rather than guess.
This is the one honest gap in the job: a non-stock part means a second trip. It's not common, but on a 10,833-household town built mostly in one decade, it happens often enough that we plan for it instead of promising around it.