This is a genuine OEM replacement part, it is sold individually. This is the threaded cap for the 5836201 Oil Tank. It is commonly used with chainsaws, and is compatible with the models listed below. This part prevents oil from spilling out, and is needed to keep the tool running properly. No tools needed for installation, simply thread onto the oil tank. Compatibility with: P540 18V Cordless Chain Saw, CS1800 18V Cordless Chain Saw, P542 Chainsaw, P541 Chainsaw, P540A 18 Volt Cordless Chain Saw, P540B 18 Volt Cordless Chain Saw, P545 Chain Saw, UT-34010 18 Volt Cordless Chainsaw