The ACS Products Brake Fluid Reservoir is machined from 6061 aluminum billet. The cap is threaded onto the body and sealed with a Viton O-ring for easy filling and cleaning. The cap and body have 1/8-27 NPT (female) threads. Reservoir is supplied with a double ended 1/8-27 NPT male fitting and a vented plug. Unit can be threaded directly onto the master cylinder port.