The CATS stock for Heat Core is for those who want a full collapsable stock for their Paradigm Pro/CQB Mk III, but with the ability to remote line to a tank.
It replaces the CATS stock from the Mk I/II K-Series and is designed to work with only with MILSIG markers that have the HEAT core install (Paradigm Pro, K-Series Mk III CQB markers, or upgraded MILSIG markers).
The nipple on the CATS stock is designed to work with any remote line that uses a standard nipple.