Genuine Honda exhaust pipe joint collar, there are 2 collars for each header. A CB550 requires a total of 8. These collars crush the exhaust gasket evenly as you tighten the nuts on the studs. These are designed to work with the stock flanges.
Honda OEM Part Number: 18233-107-000
Fits Honda: CB100K - 1970-1972
CL100K - 1970-1972
CL100S - 1971-1973
SL100K - 1970-1973
XL100K - 1977-1978
CL125S - 1973-1974
CT125 - 1977
SL125K - 1971-1973
TL125K - 1973-1975
TL125S - 1976
XL125 - 1976-1978
TL250 - 1975-1976
CB400F - 1977
CB500K - 1971-1973
CB550K - 1974-1978
CB550F Super Sport - 1975-1977