25 columns and 50 tubes; sephadex g-50, fine 2 ml column, 1.5 ml centrifuge tube, preassembled, recommended for dna greater than 72 bp, equilibrated in 10 mm tris, 1 mm edta, 0.1 m nac1, ph 8.0, for radiolabeled probes, for for use in swing bucket rotors 1100 x g disposable