Determining the size (diameter) of your caster stem can be difficult but is critical to avoid ordering and receiving the wrong casters. Take a look at the tips on this page for help in confirming the stem size that you need.

Near the end of this page is a listing of the more common threaded stem sizes. Once you have determined the diameter and threads-per-inch (TPI) of your caster stem, you can confirm if with the listing.

And remember, in the case of threaded stems, a sure-fire method to determining their size is to take a caster to your local hardware store. Find a nut that easily screws onto the caster. The label on the bin from which you selected the nut will tell you the size of the threaded stem.

Tips for determining the threaded stem size:

	Calipers are the best method to accurately measure the stem diameter. While you may not have any calipers, here's a perfect excuse to buy some. They are inexpensive and you'll use them more than you think.
	Use an open-ended wrench to determine the stem size. Grip neck stems will typically be 5/16" while grip ring stems will typically be 3/8" or 5/16".
;	Measuring a round stem accurately is difficult. Tighten an adjustable wrench onto the stem until just touching, then measure the distance between the wrench jaws.
;	Take a narrow strip of paper and wind it around the stem. Make a pencil mark exactly at the spot where the paper makes a full circle. Remove the paper and measure from the end to the pencil mark. If it measures just over 3/4" long, the stem is 1/4" diameter. If it measures just under 1" long, the stem is 5/16" diameter. If it measures 1-3/16" long, the stem is 3/8" diameter. If it measures 1-3/8" long, the stem is 7/16" diameter.
	Common threaded stem sizes: 1/4" - 20 TPI (threads per inch) 5/16" - 18 TPI 3/8" - 16 TPI 3/8" - 24 TPI 7/16" - 14 TPI 1/2" - 13 TPI 1/2" - 20 TPI 5/8" - 11 TPI 3/4" - 11 TPI

In addition, you can mail your caster to Apollo Caster and we can find a matching new one. There is no charge for this, unless you want the caster returned without ordering.