Thetford replacement Flush Knob (white) for C2, C3 & C4 Toilets. Part number 1637762. Suitable for C2, C3, C4 Models. 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 are Monday to Friday. Please be aware that if your postcode starts with certain codes, you may incur a surcharge.