Sea-Bird stopped selling SBE 13Y and SBE 23Y DO sensors in 2001, but customers who bought these sensors in the past still request us to service and calibrate the sensors. Parts for these sensors are difficult to procure because of component obsolescence. As of March 1, 2015, we will no longer service or calibrate these sensors. We recommend that customers replace these sensors with a new SBE 43 DO Sensor. Consequently, Sea-Bird is offering a Trade-In Program to provide you with an opportunity to improve your DO measurement capability and accuracy: Trade in an SBE 13Y or 23Y, and receive a 35% discount on the list price of a new SBE 43 Dissolved Oxygen Sensor (only one discount can be used per purchased sensor). This offer is valid for orders placed by March 1, 2015.