RJ11 (6P4C) jack to jack joiner. Useful for connecting two telephone cables together
Brand name(s) : Mode Electronics

Bulk packaging

Features:
Standard telephone joiners are cross connected
For example : An RJ12 (6P/6C) cross over coupler 6P/6C is connected 1:6, 2:5, 3:4, 4:3, 5:2, 6:1