Protobloc 2a rvfm rh 21b p this protobloc 2a breadboard h21b features 4 rows of 50 interconnected sockets suitable for use as power supply rails all positions are clearly defined on an alphanumeric grid p p the abs polymer board is mounted onto a rigid base plate complete with three 4mm terminals in red black and green for power connections a mounting bracket which clips into the base is also provided to accept a variety of components including switches and potentiometers etc p