1、Designed for 19mm Tubes: This test tube rack is designed with 12 holes in total, and each hole is about 19mm / 0.75in in diameter. 2、304 Stainless Steel: This centrifuge tube holder is made of premium 304 stainless steel material, and it's featured with sturdy structure and excellent impact resistance. 3、3 Tiers: This test tube holder features 3 tiers design which can hold the tube firmly and avoid the test tube damage effectively, perfect for laboratory. 4、Wide Application: This centrifuge tube rack is widely applicable to scientific experiments, plant propagation and storage of cooking spices. 5、Easy to Use: This stainless steel tube rack is ideal for laboratory, which can provide clear view of the tube contents and convenient insertion and removal of tubes.