Glas-Col's glass and PTFE stirring assemblies are designed for overhead agitation in air-tight systems with single- or multiple-neck flasks. They also reduce the possibility of sample contamination and are well suited for agitating corrosive and caustic samples. The glass stirring rod is precision ground and polished to reduce abrasion to the sealing surface of the PTFE bearing, thereby allowing a vacuum-tight seal. Each stirring rod includes a PTFE nut and bolt. Bearings (item #21051) and blades (item # 21052) sold separately.