Pack of 10 pieces, indivdual spring loaded female sockets that can be soldered into a through hole PCB. The sockets are gold plated for superior contact performance and are ideal to create a crystal socket on a PCB as shown in one of the pictures. The springs inside the socket securly hold standard component pins of crystals, resistors, capacitors, diodes, etc. These individual pin sockets also come in handy whenever you want to experiment with different component values on a printed circuit board, such as for example different R and C values in a filter. By adding these sockets the component is quickly removed and replaced with a different value.