Super Receiver by PetSafe

PetSafe says:

This extra receiver collar can be used to add another dog to any PetSafe in-ground fence system or as a replacement collar to the Stubborn Dog In-Ground Radio Fence (PIG00-10777 or PIG23-10682).

* Designed for stubborn or hard-to-train pets

* 4 levels of correction, plus tone-only option

* Uses 9-volt alkaline battery (not included)

* Waterproof