This BWR aluminum block plug is a M28 to -10 AN adapter. This fitting threads into the OEM drain-back galleys on the backside of most Honda B-series (and some D-series) engines. It’s especially useful when you are building your own catchcan breather kit and desire to eliminate the OEM black crank case breather box.
A BWR B-series block plug for eliminating the OEM black breather box is available separately and is usually used in conjunction with this M28 -10 adapter fitting when building your own catch can or even using the BWR race catch can system.
B-series engine’s require two of these fittings as shown in the last couple photos.
Price listed is for one fitting.