For this kind of call the truck carries replacement track sections in the common residential widths, nylon and steel rollers, lift cables, and the brackets that mount to older stud spacing, since houses from this era don't always match current framing standards. What we can't always carry is a match for an obsolete track profile on a door that's been patched over the years with mismatched parts - those sometimes need a specific piece ordered rather than pulled off the shelf, and we'll tell you that on the spot rather than promise a same-visit fix we can't back up. Springs, opener parts, and full door panels are stocked for other calls but aren't usually what an off-track job needs, since the fault is almost always in the rail and the rollers, not the spring system.