MerriwayBH06974 (4 Pcs) Brown Shepherd Type Ball Castors No. 16 Socket Fix, 40mm (1.1/2 inch) 180kg Maximum Load - Pack of 2 x Left Hand, 2 x Right Hand Pieces

They're a bit smaller than I expected and the rolling bits that make contact with the floor are plastic, not metal. So I'm not sure how long they're going to last.Good fit though, and an easy replacement for an original set of armchair castors that had gone to meet their maker. I just levered the old ones out of the wooden chair frame with a screwdriver and used a hammer and a nail punch on the rims of the new ones to install them into the existing holes.UPDATE: these lasted little less than two months before the metal part of one of the castors shattered, leaving the chair I had fitted them to wobbly and uncomfortable to sit in. Very disappointing. Original four-star review downgraded to two.

Good product