A little while ago I ended up coming home with a pallet full of center links. I'm not sure what a few of them go to. I've been working on getting them freed up by letting them soak in diesel fuel. The yellow one I guess came from a utility tractor and came loose easily. The green one is taking a little longer. I let them soak for a few days then give them a couple tries with a pipe wrench. So far been pretty lucky. Anyway the yellow one seems to be missing a round cover of some sort. Is it something available or does anyone recognize these two?