B&J Cage Unit - A "Trap Within a Trap" because it renews all working parts including the seat. It is calibrated for uniform sensitivity.
This B&J Cage Unit is a complete one piece thermostatic trap interior, which combines element, plug and seat. 
It is designed to replace all the working parts of the trap listed on the top of this box.  Do not use in any other trap.
Caution: Some cage units require new trap cover on first installation.