They're like $20 from a dealership, replace it every summer along with spark plugs and coolant. If you get an OE Honda one, it will come with new crush washers (the copper washers Bumnah mentioned above) which are a good idea to replace.
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Andy - Reinstated
Hybrid Forum Moderator
'06 Subaru Legacy Spec B - Stock, for now
'98 Civic EX - CTR headlights and grill, Kosei K1's, for sale
'90 240SX - SR20DET that will never get installed, project car.