Bel-Art Round 0.5lb Lead Ring Flask Weight with Vikem Vinyl Coating; For 125-500ml Flasks (F18307-0005) Vinyl-coated lead ring used to stabilize and weigh down Erlenmeyer-style flasks in water baths to reduce breakage and prevent floating and spilling Vikem vinyl-coated non-slip surface seats securely around the neck of the flask Cushioned surface will not scratch labware Fits 125 to 500mL Erlenmeyer-style flasks 3.0" (76mm) outside diameter (OD), 1.7" (43mm) inside diameter (ID), and approximate weight of 0.5lb. (237gr)