The Senza Ergo seating has been designed to function for heavy duty 24 hour usage in any task or office setting. With its extra high back and adjustable arms, Senza Ergo offers multiple enhanced ergonomic features based on how employees sit and move over the course of a day. Asynchro or PCB mechanism. Asynchro mechanism provides free floating back action, lockable seat and back. Permanent contact back (PCB) allows you to adjust the tilt of the back rest or leave it free floating. CMHR high resilience, flexible foam seats for enhanced comfort.