A magnetic device for attachment on an exterior wall of a canister where the canister is mounted within a liquid flow path. The purpose of the device is to attract ferrous particulate matter flowing within the flow path and cause that ferrous particulate matter to be fixed to the inside surface of the canister therefore no longer flowing in the flow path. The device has a frame which includes a cavity and within that cavity is mounted a baseplate. Mounted on the baseplate are a pair of blocks. Mounted on each of the blocks is a plurality of magnets with the magnets mounted in a side abutting relationship in conjunction with each block. Between the blocks is located a bridge. The bridge permits limited flexing of the frame so the frame can be used to accommodate to different diameters of canisters within about a one-half inch range.