 Bridgeport manual milling machines have come in many types and sizes over the years, including (but not limited to) the C head (original), R head (heavy duty C head), M head, J head (and high speed, 5440 RPM version), 2J1 1/2 head (1.5 HP Vari-Speed), 2J2 (2HP Vari-speed), and Series II head (4HP Vari-speed).All of the heads offer variable speeds, the earlier ones via a step pulley (cone pulley) and the later ones via either continuously variable transmission (CVT) systems or variable-speed drive.Typical table sizes are 9″ × 49″ (Y and X, respectively) and 10″ × 54″.