These Class A PYREX® volumetric flasks have machine-blown bodies to which are sealed heavy-beaded, heavy-tubing necks, tooled for Standard Taper polyethylene stoppers. The linear high density polyethylene stoppers are made with a closed bottom to conform to Standard Taper stopper dimensions. For replacement stoppers see No. 7624. The graduation line is sharp and permanent and large white block letters make the inscription easy to read.