I took a real close look at one of these sockets at the auto parts store today---They are designed so that the wire, contactor and spring all set in a thinwall brass tube, which in theory is supposed to slide in and out of holes in the plastic part at the rear of the socket. The length of the holes in the plastic part are supposed to give "linear guidance" to the brass tube, the spring and the wire which has the contactor on the end of it, thus keeping them from cocking sideways and shorting out against the socket. They are not intended to have the "fibre disc".----Nice plan, but by the time they loosen up all the tolerances to mass produce these things, the tubes and wires still cock sideways and short out. This is supposedly TECHNICAL ADVANCEMENT.