This is simply the best system we have ever come across, as it uses no weights whatsoever - the same principle as used on the more upmarket washing machines. A circular tubular ring fits behind a hub cap. This is filled with silicone and some large ball bearings. When a wheel goes out of balance through picking up a stone etc. the balls move to counteract the imbalance. The system is imported and fitted by CMCA member Bruce Riley - a specialist truck wheel aligner and proud owner of a magnificent American Eagle Coach Conversion. Bruce gave a marvellous talk on suspensions at the Roving Members August get together at the CMCA Casino Village.