... temperature resistant 50,000 hours no burning Specification of glass test tube stopper(mm) Φ 12 (9*13) Φ 13 ... 12, Φ 13 etc, means external diameter size of test tube, size in bracket is to be adjusted.Features ... as below: 1. Applicable to each different aperture test tube and triangle flask, having wide size range ... to growth of any bacterium, biological cell and virus, and is the same as cotton stopper ( ...