Rail Hopper Cars Valves & Cylinders Protection Box This unit is a 1/4" thick cast aluminum construction. The enclosure integrates the directional control valve (Super Spool™), subbase and a protection box all in one unit. Some of the advantages of the Bosch Rexroth enclosure are that the lid will remain closed (with the use of heavy-duty latches) if the car is used in rotary service. You will also have the option to lock the box. If the lid is left open, it will automatically shut when the cars hump. You will have enough room at the end of the box to trip the manual overrides with a gloved hand. The diode box can be replaced without removing the valve. Again, these are just some of the value added features that are included in the Bosch Rexroth design.