Bolt in zinc anode for your Spex MX-5 C&R radiator. The C&R raditor was designed with 2 weld in bungs for a water pressure sensor and a sacrificial anode.
The intent of the sacrificial anode is to give any electrolysis a sacrificial soft metal to corrode instead of the Aluminum in the radiator and other locations throughout the engine.
Anode bolts right into place without any modification.