Massive bakelite tube socket PL3-1PD56 (ПЛ3-1ПД56) was designed for tube type GI-30 (ГИ-30). This tube socket is also usable for 6S41S, GU-29, GMI-6, GU-32 etc. The upper spring is easily removable, it just serves for the GI-30 tube fixing, but the four side tin sheet metals are riveted into the socket, however these are really thin and flexible, so after its removal or adjustment is the socket usable also for 6S33S and 6S18S tubes. Electrical operational limits: 2,4A, 1000V. Operating temperature range is from -60 up to +150 Celsius degrees. Minimum service life: 15 years (without crossing any prescribed limits). New old stock sockets made in the 70's and 80's (please see the gallery).