Thetford Vent Button Assembly - Yellow for the C2, C3 & C4 and C200 cassette holding tanks. Part 21 in the picture isn't made as 2 parts anymore. The rubber part is now been moulded to the bottom part. We aim to ship all orders on the same day if they are ordered and payment has cleared before 3 pm or within 1 working day after 3 pm by your chosen service (working days Mon - Fri, available delivery services are postcode dependant. Please be aware that if your postcode starts with the following you may incur d