18291-283-000 (18291-ME9-000) exhaust gaskets are by Vesrah. They measure 44.20 x 52.00 x 4mm, and fit the following bikes:
(sold individually)

'75-'76 CB500T
'70-'74 CB450K3/K4/K5/K6/K7
'70-'73 CL450K3/K4/K5/K6
'84-'85 VT700C
'74-'75 XL350K1
'76-'78 XL350
CB450K1/K2
'83 XLV750RD