http://store.matrixbb.com/servlet/-strse-28128/TSD-BE-Full-Metal/Detail
if you don't plan on spending $100+ on a GBB, don't ask for reliability advice. the answer is "no it's not"
i'll tell u one thing, I got the TSD iron sight set for the HK416, the metal wasn't up to par, it wasn't finely milled, and the paint job was lackluster.