If you’ve been running the default SL viewer or updated to the new Firestorm release you’ll have noticed a new feature called avatar complexity. See Inara Pey’s excellent blog post for details
Fear not! All [TMC] shoes and collars have an avatar complexity of less than 3000 (and most are closer to 2000) which is very low so you won’t be turning to jelly! I’ll be adding the avatar complexity to market place listings so you can see exactly what it is.