Alloy filler neck.
Can be welded, brazed, or soldered to any brass, steel, alloy, or stainless steel radiator or expansion tank or pipe.
Available in 2 sizes:
standard radiator cap 11/4" opening ID with 1/8" breather
Japanese ("mini") taking 32mm radiator cap with 1/16" breather
Special valveless radiator cap (non vented).
Designed for use on vehicles where a radiator or expansion or header tank cap is required which has no opening pressure valve.
Useful for modified cars which require a non-vented cap somewhere in the plumbing system.