The sumo strength weight vest inserts are designed to last, with strong steel and powder coating they will withstand whatever you throw at them. the sumo strength plate inserts are designed to fit inside the sumo strength weight vest plate carrier (wvest2). with the sumo strength plate inserts, you can create competition standard weight vests! Using the 4kg/8lb or 2. 5kg/5lb inserts paired with the sumo strength plate carrier, you can create a 9kg/20lb or 6kg/15lb weight vest.