For Test Tube 18 x 150mm
Top Diameter: 19 mm
Bottom Diameter: 14 mm
Length: 25 mm
Approximate Number Per lb: 53
Developed for demanding laboratory work. Soft, pliable, resilient, low in free sulfur, resistant to chemical attack. Made of black or blue rubber. Size numbers are molded into the top. 

NOTE: Bottom of stopper diameter must be smaller than test tube diameter.