Our magnetic stir bars are constructed of high quality magnets coated with PTFE. Along with individual sizes of polygon, octagon, and egg-shaped, two convenient assortments are available. Stir bar retrievers also available. Item # Description Dimensions (Length x Diameter) MSB15 Stir Bar, Octagon, with pivot ring 15mm x 7.5mm MSB25 Stir Bar, Octagon, with pivot ring 25mm x 8mm MSB35 Stir Bar, Octagon, with pivot ring 35mm x 9mm MSB40 Stir Bar, Octagon, with pivot ring 40mm x 8mm MSB48 Stir Bar, Octagon, with pivot ring 48.5mm x 10mm MSZ12 Stir Bar, Polygon, without pivot ring 12mm x 3mm MSZ25 Stir Bar, Polygon, without pivot ring 25mm x 8mm MSZ40 Stir Bar, Polygon, without pivot ring 40mm x 8mm MSZ70 Stir Bar, Polygon, without pivot ring 70mm x 9mm MSHL15 Stir Bar, Egg-shaped, blunt edges 15mm x 7mm MSHL30 Stir Bar, Egg-shaped, blunt edges 30mm x 13mm MSHL50 Stir Bar, Egg-shaped, blunt edges 50mm x 20mm MBR350 Magnetic Stir Bar Retriever, 350mm long - MSBA20 Magnetic Stir Bar Assortment, set of 20 (2 each of all MSB series bars, plus 2 each of MSZ12, SZ70, MSHL15, MSHL30 and MSHL50) - MSBA50 Magnetic Stir Bar Assortment, set of 50 (5 each of all MSB series bars, plus 5 each of MSZ12, MSZ70, MSHL15, MSHL30 and MSHL50) -