Old post, but what are these (for), price and where did you get them?
What they are is a long blab.
They're a 4mm brass measurement tool for installing a servo pulley to exactly that height off the deck. The pulley is steel and the deck is aluminum, and it's weirdly adjustable by friction kinda like a choke? The more you tighten it down the lower it travels. I've seen guys pitch a fit trying to get the right measurement (without the tool) and one guy offered grease "so it will come off easier" WTF I don't know all that much but you don't grease a friction fit part. Especially one thats main purpose is to spin at high rpm.
So you can either wing it with a 5mm allen and hope to get the 4mm height AND get the 5mm out of the thing. Or use the brass and it will slide out much easier. Never really had to use it, servos don't fail that often unless they let an FNG mess with the CCF box.
Cost, I don't know, they are work issue. Ordered them because I like brass.