High impact plastic but not sure they'd be quite as durable as the Sennheiser set, which are metal cased

It's an excellent moderately priced wireless lav system that's just as good as the Sennheiser or anything else we've rented

For those cases, you'll want to either rent gear or save up the extra $200-400 for a good sennheiser kit with multiple transmitters and lav mics

I sometimes get dropouts in location situations, however, and the range is very limited because the Sennheiser portable receivers are not diversity systems.