Good-bye backaches. Save your sacroiliac with a 3-wheeled professional mover's dolly. It measures 6-3/8" wide between a trio of swivel casters with 1-9/16" x 11/16" wheels, and has a drop-down center and a 1/2" dia hole for permanent attachment to frequently moved items. Steel construction, 110 lb max load (so not piano-duty), and rubber pads above each wheel. Stands 2-1/2" tall. We think ordering (4) would be a good place to start.

These light-duty plastic casters are on swiveling stems and have dual 1-1/2" dia x 5/16" wheels in 1-7/8" x 1-3/16" hemispheric housings. Stems are striated steel, 3/8" dia x 3/4" long. We're thinking these would be fine for your average chair. Our each is a bag of (4).

These little swivel-plate casters look like they should be on the bottom of one of those spinner carry-on suitcases. In flat black, they have (2) 1-1/8" dia x 3/8" plastic wheels (approx 1-1/4" thick) on a 1/4" stem and a 1-1/8” square steel plate with 3/16" mounting holes at the corners. Make a rolling file, or your own  spinner luggage.

These small swivel plate casters have dual 1-3/8” dia plastic wheels on coincidentally 1-3/8” square mounting plates with (4) holes. Measure just under 2” tall and are screaming to be used to make rolling plant holders, because nothing is more boring than plants that just sit there in one place all the time. They have a little dirt on the wheels that cleans up nicely with some soap and water. That's Surplus for ya'.

Our 4" dia swivel-stem casters have 3/4" wide dual black-plastic wheels and 1" steel stems with 1/2" - 13 threads. No weight limit listed, but they're pretty sturdy, and pretty snazzy, at least to the extent that casters admit of snazziness.