For incubating in baths or vessels at elevated or reduced temperatures (-70° to +100°C) White, polypropylene racks that float, but suspend entire microtube in liquid Built-in handle and legs for easy handling in bath or on bench Autoclavable racks take 1.0, 1.2, 1.5 and 2.0 mL tubes. 2591C36 has 20 places and are 3 3/4" in diameter. 2591C38 has 8 places and are 2-3/4" in diameter.