I just got a new "58" Remington by Uberti, in 36 caliber. I checked the nipples and they are the same as Uberti uses in the Colt models. (And the 2nd and 3rd gen Colts). The thread is #12-28, the same as Ruger, and the ROA nipples will fit. They are about .015 short, and need a small shim washer, .015 thick, .216 ID and .31 to .36 OD. (.313 is 5/16 dia, so could part off of brass stock on a lathe after drilling the #12 clearance hole.) Or turn 3/8 down a bit til it fits in the nipple well. If you want good stainless nipples, Ruger, or aftermarket Ruger is a source. Of course, you'll need a Ruger nipple wrench. (3/16 nut driver). Check your cylinder, however, as I have an older Uberti 44 that has much different threads.