when i get a chance i will measure them .I haven't measured them out but my guess is standard 1/4" id x 3/8" od
thank youManufactured by DANCO Stock number 35870B, #90 O-ring 1/2" O.D x 1/4" I.D. x 1/8" H.
hard to lose the o ring but i had one split and two get hard and frayed a little . lucky i always have a few sets on hand .Cheers for that, Added to my shopping list. Never know when you will lose one of those little guys.