Shakes an entire rack of test tubes at once. One or two holders easily mount on the Benchtop Shaker head. The holder can be rotated through 180° and fastened at any position within the rotation for ease of loading test tube rack and adjusting shaking action. Racks are held in place by a restraining cover. This cover automatically releases and remains captive when retaining nuts are loosened for rack insertion or removal. Accepts test tube rack up to 12 x 5" with capped or stoppered tubes from 75 to 200mm long.