While using my orange Lyman 55 powder measure today I noticed that the opening at the top of the reservoir looked about the same size and the opening on a 1 lb. bottlo of Clays powder. I tried the Clays lid on the powder reservoir and it was a close fit. I believe if the threads were ground off it would be a good fit. I found another metal powder bottle lid that did snugly fit a gray Lyman 55 reservoir. I have the Lyman metal lids for both of my 55s so won't need to improvise. You see a lot of 55s on sale boards that are missing the lids; don't let that keep you from buying one (or a spare) if the price is right. This may be old news but but it's news to me.