Unior sprocket wear indicatorthis tool can be used to check the wear of 12 21 tooth sprockets this had typically been difficult to measure accurately worn cassette teeth will quickly wear out your chain and create issues in shifting or the ability for the chain to stay in gear the chain is put on the sprocket and the tool placed with its round end between two teeth on the upper sprocket side the last chain link is moved away from the sprocket and a force of 100n or 10kg is applied to the tool