Non-volatile data memory cards, flash drives and other memory devices are customized by manufacturing core memory units all the same and then covering them by outer skins which may be made to have different appearances andor tactile characteristics. The present invention also relates to methods of using such filters. A lock rod 35 reciprocating in an about right-angle direction to the piston rod 18 is built into a lock cylinder 33 provided in the cylinder body 23. Since a circuit substrate is hermetically sealed and housed within the housing, there is no possibility that pressure during vulcanization is applied to the sensor.