For No. 779-400-11 and 779-450-11. Accommodates various size and shape containers or test tube supports. Can hold six 1000 ml or two 4000 ml Erlenmeyer flasks. Aluminum box is 18"" x 12"" x 4"" deep inside. Slots in all four sides for rubber-covered crosswise and lengthwise bar clamps (Nos. 779-500-04 and 779-500-06) which can be simultaneously used. Bar clamps are secured by wing nuts. Supplied with one crosswise bar clamp and 1/8"" thick rubber pad for bottom.