ADD-ADPT-STFSTF-SD is a Fiber Optic Adapter, used in fiber optic links to provide a cable-to-cable fiber connection. Specifically, this adapter has two female ST connectors on one side, and two female ST connectors on the other. ADD-ADPT-STFSTF-SD provides connection between two male ST SMF Duplex cables. _x000D__x000D_AddOn Adapters are 100% compliant for all of your networking needs. Now you have a cost effective solution to your network upgrade needs.