Abstract: The present invention improves performance of a flask used for microorganism, cell and tissue culture. The flask is composed of culture chamber, a wide oblong opening and a closure unit. The wide oblong opening eliminates the bottle neck restriction of conventional flasks and gives easy access to the culture chamber. The closure unit is constructed with a snap-on closure, a base and springs, which interconnect the closure and the main body of flask through the base. The springs function to maintain the closure at the opening position to facilitate culture operation. The problem of the screw-on closure that requires to be hold in a operator's hand is solved.