What the gurus here have said is that as long as the beads are at least 3mm or larger, you shouldn't have a problem.
I haven't had a chance to use the plastic pellets that kids use with rock tumblers because my cats have only recently started using the LF (they had a longshoreman's strike against the new device but are now starting to give in and return to work

) but when it comes time to replace the granules, I'm going to try them unless LF is back in bidness by then.
I refuse to buy granules for $75.00 on EBay!