Generation IV External Engine - help! mystery o-ring!

ok so i got a little drunk during the disassembling of the engine and now i found this little guy on the floor of my garage. anyone recognize it? that is a quarter to reference its size. any input or thoughts are appreciated

http://i1068.photobucket.com/albums/u448/nolson70/DSC04937.jpg

Looks like the coolant cross-over pipe o-ring.

u are correct!. thanks

Looks like the coolant cross-over pipe o-ring.

youre good!!!:D