High Fives to Coffinmaker on his post with a few added comments. Most if not all of the aftermarket nipples do well with Rem 10's. They have the proper dimensions to fit over caps, fit snuggly, and have the longest outside petals to fit over the nipples. CCI 11's are next, followed by RWS 1045's. Rem 11's have shorter petals, shorter than Rem 10's, CCI 11's, and the RWS 1045's in that order.
What Rem 11's I have used, and they were holdovers from my percussion TC caplock rifle, the Rem 11's didn't fit as tight and fell off of the nipples more than the others after firing due to having shorter petals not adhering to the nipple. This can be bad if the cap fragments fall into your revolver action. Using the three others I mentioned, they still fit tight enough to stay on the nipples after firing for the most part, just needing a flick with a fingernail to dislodge.
CCI 10's are a tight fitting cap, on most nipples with a few exceptions require hard seating and, in my experience, fail to even seat firmly some on caps, either original or aftermarket. Avoid them if possible. Many have written of this. Too tight of an inside dimension and shorter outside length petals. I have probably 475 of the 500 I bought some years ago before knowing of the dimension of them that I have no use for. I had to use a wooden dowel to seat and gritted my teeth hoping I wouldn't cause them to fire. Wouldn't be a harmonious outcome.
As Coffin suggested, buy when you find, but watch any seller that is really trying to scalp ya. A good posting on this forum can be found on the Darkside section. At the top you'll find the Dark Arts. Click on that, go around 2/3's of the way down and you'll find a thread posted by Mako titled 'Cap Gun Primer: Correct Cone Length' (cone--another word used by some for nipples). Around 4 pages long, Mako gives very good CAD pictures, explanations, and charts of the use of various nipples and percussion cap relationships. There is a very informative chart showing the dimensions of available percussion caps available. This was posted before SlixShots, but Slix's, Treso's, and Track of the Wolf nipples are all pretty much the same in size but differ in material and a few other construction this and that. FWIW, nipples and caps pretty much follow the same sizing requirements and need be the revolver be a Uberti or Pietta. A Ruger Old Army pretty much has its own sizing, but the Rem 10's in my shooting are the best also.
Factory nipples pretty much IMO and experience follow the same cap/nipple relationship as the aftermarkets with a few exceptions. I've found when comparing all of the nipples I've mentioned and brands/sizes of percussion caps Rem #10's are the best followed by CCI 11's, then RWS 1045's. IMO due to the shortage of caps being offered by retail outlets, if ya find some of the three I mentioned as being the best, invest in more than ya think you'll need, if not you'll be on the search for more after the one or two tins ya buy at the time are shot up. See the Professor chimed in, don't agree with that approach and method, but he is a good guy.