Material: Polystyrene Capacity: 50 Tubes For tubes with an OD ranging from 15mm to 17mm Ideal for many applications around the house, including parties, arts and crafts, and so on 50-Place Test tube rack for 15/18mm diam. Tubes, detachable, plastic, Color is CLEAR. Test tube rack is manufactured to hold 50 tubes having an outside diameter ranging from 15 - 18mm. Great to hold tubes for parties, lip balm kits, essential oil preparation, etc.