"I have several vacuum variable caps by Jennings. They are all in the 300-20pf range and work just great. I recently saw a 50 lb Jennings unit at Gaithersburg! It was a .002ufd 50KV variable vacuum cap! I have never seen one that big before. They wanted $150.00 for this beauty, but I had to pass it by. Vacuum variables work just like any other cap only space is the dielectric." That .002ufd 50KV for 150.00 was an incredible bargain! Ed Phillips