A rigid high load lightweight block has unidirectional high strength moulded fibre bundles in the side plates for the carrying of the major operating tensile loads within the block, thereby minimising the weight and maximising the load of the assembly. A plurality of arcuate brush seal segments 16 may be retained in the plurality of arcuate labyrinth seal segments 14, thereby forming a combined labyrinth and brush seal. The linear actuator further includes a magnetic sensor that detects a position of the coil body along the lengthwise direction of the coil body with respect to the multipolar magnet, and an electrifying control circuit that individually controls currents to be supplied to the plurality of coil units based on the position of the coil body detected by the magnet sensor. The elastic fiber layer has a high friction surface such that an end of a glove pulled over the elastic fiber layer is inhibited from rolling or sliding back over the elastic fiber and down the sleeve. Furthermore, the architecture of the illustrative embodiment ameliorates the well-known add-before-drop problem.