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).

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 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.

Our 4" dia swivel-stem casters have 3/4" wide dual black-plastic wheels and 1" steel stems with 1/2" - 13 threads. Available with or without a foot-operated lock No weight limit listed, but they're pretty sturdy, and pretty snazzy, at least to the extent that casters admit of snazziness.

This set of (4) stylish gray plastic casters includes (2) fixed and (2) swivelers. All have double 1-1/2" dia x 1/4" wheels set on an axle and are 1-3/16" wide overall. Fixed caster plates are 2-7/8" x 1-5/8" with 3/16" mounting holes on the corners and a tooth on the long side; swivel plates are1-5/8" sq with 3/16" mounting holes.

These ball casters are great swivelers and quite snazzy looking, too. Seen on your better chairs everywhere. These are brass plated, 2-1/2" dia on 1-1/2" square mounting plates with 3/16" holes at the corners.

For people with a heavy load, or folks who just like to make sure, we confidently offer our heavy-duty air cargo/conveyor swivel-plate casters from Faultless®. Rated for a 375-lb load, their Polyflex wheels with needle bearings measure 2-3/4" dia x 1-3/8" wide on 3/8” axles with thread guards. The 5-3/8" dia x 2-3/8" toe guards are on 4-7/16" x 3" mounting plates with 5/16” holes, and the wheels extend 5/8” below the toe guards.