The upper coolant neck sits between the rear of the engine and the firewall, and this billet adapter routes the piping towards the front of the engine.
Allows for a clean easy setup, and not having to deal with finding a long irregular shaped radiator hose.
This billet water neck is for the PRB K20 cylinder head only.
If you are using the complete K24 long block, you need to use the RBB Water neck for RWD K-swap setups.
Comes with 5/8" hose barb for heater hose.