Adjustable spinner height. Ptfe impeller assembly rides on glass bearings for friction free operation. 25ml & 50ml have black phenolic rubber lined caps. 100ml-300ml have polypropylene caps, silicone gasket and pouring rings. Black phenolic rubber-lined caps Flask has flat bottom (no dimple) Center (mm):38 Sidearm (mm):18 Od x oah (mm):38 x 120