Cam Angle Sensor Disk for Nissan RB25DET, VG Series and some RB26 Nissan engines (50mm OD. Use this disk if you have an EMS and need to run a different CAS. New Series 2 30-6610 and 30-6620 kits include this disk and do not require it to be purchased separately. If you are buying your EMS second hand (used), or have a Series 1 EMS, you may need to buy this disk if you are having "sync" problems. This disk is a direct replacement for the factory Crank Angle Sensor disk, and the center of the disk should look exactly like the stock one in your distributor.