This is a replacement master cylinder for a model 10 or 20 drum brake surge coupler manufactured by Titan / Dico.  Fits all Titan / Dico model 10 or model 20 surge brake couplers.  This master cylinder is designed to work with drum brakes.  Its an easy bolt on installation for replacing your old worn out / blown seals master cylinder.  Comes with everything pictured: the master cylinder, boot, lid, gasket, and cap.  Titan part number 2374400