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.

You’re on a roll. You’ve been on a roll for years and you know it. Keep it going with this set of (6) 5/8" dia steel ball casters on 2" x 1-3/8" plates with 5/32" mounting holes. Rated for a max load of 35 lbs, and come on, you’ve got a million things under 35 lbs that need rolling.

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.

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.