Further, seal means such as in the form of first and second annular seal elements, or O-rings, 58, 60 may be provided for seating in each of the opposite ends 20A, 20B of the housing 20 for creating respective seals between the opposite end support members 26, 28 of the core 16 and the housing 20 and between the removable end closures 22, 24 and the housing 20. (Only the first and second seal elem