i use this caps with the Pedersoly 1857 Mauser, and i love them. No misfires and very reliable.
if you are not using shooting glasses, then you should either close your eyes, or not buy this caps.
When the hammer strikes the cap, there is a little debris that will fly off the cap and hit you in the face, but thats what shooting glasses are for (if you use a flint lock rifle, then you will have little pieces of flint flying everywhere). If you are a reenactor, then you are supposed to close your eyes.
anyways, i never had a problem with this caps, so i will rate them for their reliability, and my experience with them.
ps: This caps say number 11 on the description, but they are way too big for a Thompson center #11 nipple. these caps are good for bigger european nipples.