Caster; Twin; Swivel; 2-3/8" (60mm); Polyurethane; Stemless; Black; Rivet Brng; Wgt Cap: 100# (Receives Shepherd 0.35" x 1-1/8" stem) (Item #69772)

I had been searching for stemless casters for my 3rd Herman Miller Ambi chair (great chairs!), when I found Apollo Caster. The stem on the Herman Miller Ambi base is not designed to be removed. If you replace the base, the stem is on the replacement base. This comes from the service manual for this specific chair. After looking around on Apollo Caster's site, and getting a very useful reply from their email support, I ended up calling them and spoke with one of their reps, Matt. He was really helpful and patient, especially since it was such a small order. I had measured the stem the best I could without a caliper, and we both thought the casters that receive a Shepherd 0.35in x 1 1/8" stem would work. This size is the key, and it appears to be just right. I bought 2 3/8" diameter wheels, instead of the 2", but the 2" wheels with the same stem specs of 0.35inx 1 1/8" should work fine too. Matt said the larger 2 3/8" wheels would roll a little easier, and I beleive this is correct. I also like that it gets the center of the bottom of the base off the ground a little bit more. I pulled off the old wheels fairly easily by hand. However, to get the new wheels on, I used a piece of wood, about a 2 foot long 2x4, and a rubber mallet; which is the method I believe I learned from the Apollo Caster website. I tried to keep the wood solidly placed against both wheels when attaching each caster, to spread out the pressure from hitting the wood with the mallet. I had to whack the wood pretty hard to get them on, and was concerned I'd break the wheels....but nope, they ended up fitting great. Once they are solidly on, they spin very freely, and don't come off when the chair is lifted off the ground. Even better, I am really happy with these new wheels. They are quieter, roll very easily, and the polyurethane material appears to be OK on vinyl or hardwood flooring (I am currently using them on vinyl plank glue-down flooring). Thank you Appllo Caster, and especially Matt!