Surge Tank 12 oz std neck. Small Surge Tanks – Designed for lower volume cooling systems. The small tank, 12 oz capacity, comes complete with billet radiator neck and mounting bracket. Dimensions = 2.50 OD x 4.75 Tall w/ 3.0 center to center bolt spacing mounting bracket. Custom-built by C&R the aluminum surge tanks provide an additional option and the best to filling closed cooling systems and removing damaging air pockets. The sight glass option allows for better view when setting and checking proper water level is available in both models.