They come in 54 cal but not 58 cal.
I tried them just cuzz I hate dogma, but found they're a bad deal, at least in our climate.
Under the best of circumstances (brand new box just opened) ignition was okay with #11 caps.
After a couple of weeks sitting in my dry, heated storage area, ignition turned really erratic. Some delays, even a few failures to fire. Sounds changed from shot to shot and even got some fireballs. All pretty sure signs of lots of variation in ignition, even without turning on the chronograph.
Switching to musket primers helped eliminate the failures to fire, but I still got a couple of fireballs.
After two months in dry storage, the remainder of the pellets failed to fire. Period.
Those things were designed for best performance with #209 shotgun primers. They also have to be kept really, really, REALLY dry in storage if you live in a humid climate. The only way I can see that I could use them would be to store the box in a ziploc with desicant packs.
Way too much trouble and expense for something that isn't going to work as well as anything loose, whether real black or another sub.