These Pyrex® flat bottom reusable culture tubes are ideal for plant tissue culture and general culture work. The flat bottom facilitates use with agar slants. Walls and bottoms are of uniform thickness. The tubes are rimless for greater convenience in plugging and rack storage.Optional polypropylene two position closures (Cat.Nos. 1-26794-25 or 1-26795-25 for 39mL, 47mL and 59mL; Cat.Nos 1-26798-40 or 1-26799-40 for 130mL) can be opened for gas exchange or closed for humidified environment. Internal drip ring minimizes contamination.