Egg-shaped stir bars have oval magnets-ideal for use in round-bottom flasks. Shape conforms to flask bottom and ensures complete mixing. Super-strong Alnico V magnets remain coupled to drive magnets-resisting spin out at high stirring speeds. One-piece coating of PTFE resists corrosion, heat, and cold. Chemically inert stir bars won. Low-friction PTFE coating ensures smooth spinning and maximum energy transfer.