Used for active connection between two optical fiber connectors, including ST, SC, FC, LC, SMA, ST-SC, ST-FC, ST-LC, etc. Among them, ST, SC, FC, LC, SMA and so on are the same kind of type connection (Mating sleeves) , ST-SC, ST-FC, ST-LC and so on are the different kinds of type connection(Hybrid adapter).ST, FC have D shape, rectangle, square, SC, LC have a single, double, four, can meet the needs of different applications.