I'll add to Eric's good reply that a mock (or real...) lug/sleeve can be made with two tubes very easily. The outer tube (the one which is the "lug") needs to be 1/8" larger in diameter then the inner tube (the "frame tube") and have a .058" wall. This results in a near perfect sliding fit suitible for both brass and Silver practice. So a "frame tube" of 1" diameter would need a "lug" tube of 1 1/8" x .058" wall. Here's a link to Aircraft Spruce, a source for said stuff. Andy.

http://www.aircraftspruce.com/catalo...tubing_un1.php