Stirrer Blade, PTFE, Banana Shaped, Solid, 19mm, Heavy Duty, for 22000mL Flasks, 55/50 minimum joint clearance. Blade is shaped to resemble the contour of a round bottom flask. Made of 3/16" PTFE to fit 19mm OD stirrer shafts. Minimum joint size listed is the size required to allow passage of the blade.