There are three kinds of FC fiber optic adapters, flange type, Square Type and D type, FC fiber optic adapters are with plastic or metal housing, ceramic sleeves, Simplex and duplex versions.

FC hybrid fiber optic adapters are available with both plastic housing type and metal housing type
(Zinc alloy with Nickel plating). Hybrid adapters are available in singlemode and multimode and
many different configurations. They can be practically used in any application and connect different connector types.