A filter assembly including first and second mating parts and a seal received in a groove of the first mating part. The seal includes a main body and a resiliently flexible, sloping skirt that extends from one side of the main body to a distal end spaced from the main body. The seal is sized so that the resiliently flexible skirt normally extends out of the groove of the first mating part when the skirt is not biased towards the main body. When the first mating part is slid against the second mating part, the second mating part causes the distal end of skirt of the seal to be biased into the groove and towards the main body of the seal.