these look like theyll be fine for blue leg hermits
http/cgi.ebay.co.u...e=STRK:MEWAX:IT
Quite a few of those aren't useable by most hermits. Many are, but there are some odd ones in there. The price is certainly nice. The only thing that bugs me about buying shells that way is that those look like the sort where snails were probably harvested in large quantities for ornamental shells (curio trade and all that). Otherwise there probably wouldn't be cowrie shells in there, since that's a really strange one for hermits. Not to say I haven't picked up a few bags of shells like that from time to time out of desperation trying to find the right size/shape of shells for odd animals, but it's worth being aware of where they're coming from. I always prefer to check LFSs for any empties lying around from shipping casualties, although it's rare to be able to haggle them cheaper than the ebay listing you found there.
Regarding figuring out whether the shells are suitable, look at how narrow the apertures are on many of them - that's the type of shell that really flattened hermits like Ciliopagurus strigatus take. Long narrow openings are simply not possible for the common Clibanarius and Calcinus species to get their bigger behinds into unless the shell is so big relative to the animal that it is very difficult or impossible to move. Some of those shells are from cowries, and not even Ciliopagurus strigatus will take those a lot of the time (sometimes they do, but it's rare). Clibanarius species like C. tricolor require rounded aperatures. Unfortunately, if in a stressful situation, they will sometimes try to force themselves into shells that are the right size but have an ill-fitting aperature, which can lead to them getting stuck. A stuck hermit can easily be a dead or seriously injured hermit, so it's not worth risking.
Shells from that set that look suitable for the average Clibanarius/Calcinus hermit:
- bottom left Trochoid shells
- bottom middle pearly shells (might be Margarites, hard to tell)
- middle left Nerite shells
- uppder left and middle Cerithid and Turbinid shells
I have seen large Clibanarius species inhabiting shells like those on the upper right, but they ditched them at the first opportunity for rounder whelk and Turbinid shells. The rest I would not even put in the tank unless there are Ciliopagurus strigatus hermits about as well. Even then, I'd leave the cowrie shells out.