Nice quality, very light - A-Zoom Blue Revolver Snap Caps

These are very nicely machined and excellent quality.

I think these are great for dry fire practice if you are concerned about your firing pin, but for reloading drills they may be too light to develop accurate muscle memory. These are considerably lighter than a live round.

I've had other a-zoom snap caps last a very long time, and these appear to have the same material in the primer pocket, so I'd expect you'd get great life.