4" Diameter Heavy Duty Stem Caster With Stainless Steel  5/8" Stem for mounting. High Quality New 4 Piece set. These are are great quality Caster sets they were made for the food and industrial applications  industry rolling Stainless Steel carts that were very heavy and where designed to move quietly and smooth at the same time. High impact plastic wheel hubs and a very durable rubber cushioned for concrete surfaces where the rubber meets the surface that can be rough or smooth and these will roll very nice. Has a super wheel lock that stops the wheel from moving. The stem is a 5/8" diameter Stainless steel pin type that fit in the carts tubing that had a thrust bearing for swiveling. I'm not sure about the load rating but I'm guessing these will support at least 300# per caster or more the chrome caster cage is 1/8" thick and very strong steel not like a cheap imports these casters will last for years under heavy use.   If you need to use with swivel on a cart or anything moving you can just get 5/8" thrust bearings (very cheap) with washers and just insert them on the 5/8" stem and you will have a quality swivel caster.  I have plenty of these sets and if you need more just let me know and I can give a better price for multiple units or sets.