MEI Air Disc Brake Calipers are identified by the part number which is marked on the ID plate. After a long life in service or while still on the vehicle it can be difficult to read the information on the ID plate. Therefore the following can be useful in assisting identification.
Check the air chamber mounting angle. This can either be 0 degrees or +81 (NR225).
Measure the distance between the centre of the guide sleeves. It will either be 305mm (NR225 or NT225) or 264mm (NV225, NX225, NV195 & NX195).
Measure the width of the pads. They will be either 250mm wide (NR225 or NT225), 216mm wide (NV225 or NX225) or 210mm wide (NV195 or NX195).
Check the carrier - there will be 6 x M20 bolts (NR225, NT225, NV225 & NV195 or 4 x M18 bolts (NX225 & NX195).
Next, check if the Long (or Fixed) Guide Sleeve is on the Left or Right as shown. Please note that the N Series radial calipers have 2 long guide sleeves.