A heavy-duty tire comprises two rows of middle blocks. The substrate is pressed against a polishing surface on a rotating polishing table. The lock mechanism may include a lock sleeve that is biased to a normally locked position and driven along the axis by the actuator shaft when the button is depressed. The server posts a first notification to a first notification queue, in response to receiving the request. The balanced exhaust valve can be configured to selectively flow fluid between the exhaust and the respiratory interface.