EZ-Fit ST To ST Coupler ST Fiber Optic Adapter ST-ST Simplex Singlemode & Multimode Coupler With Red Dust Caps 5PCS ST To ST Coupler/ST To ST Fiber Optic Adapter Male or Female: Female to Female Dust Caps Color: Red Body material: Metal Applications:Test equipment,Connection of optical links in optical active devices,Jumper connection,Production and testing of optical devices,Optical fiber communication system, CATV, LANs and WANs, FTTX