Selling casters over the phone can be tricky especially when you don’t know exactly what stem you have and what size it is. Typically you have three different stem options when it comes to casters, see below for the following options:
Methods on how to measure a stem
Method #1: One of the biggest mistakes people do when measuring a threaded stem is they stick a ruler/tape measure to measure the diameter of the stem. This is NOT an accurate way to measure the diameter of a stem. For method#1 I would recommend using a caliper. Calipers are very accurate and will give you proper dimension.
Method #2: If you don’t have a caliper and you are measuring a threaded stem go to a local hardware store and find the nut that threads on your caster.
Method#3: Go out and buy a screw and bolt gauge. The picture below is a good example of what they look like, simply just place your stem inside the hole of which is the most snug.