How to Identify Assembly numbers And Part numbers

In order to facilitate the identity of groups of parts, a “bearing assembly number” system is used. AP bearings are each assigned a five digit numeric code that follows the cone part number to describe the individual component parts, prelubrication, performance codes, and internal clearance of the pre-set assembly. In some cases the code may be alphanumeric, although the first digit is always “9”.
For new applications, an assembly number is assigned on receipt of the first order. It is very important for the correct fitting and functioning of the bearing that the same assembly number is quoted for all subsequent replacement orders for that specific bearing position. Standard and supplemental assembly numbers are listed in this catalog starting on page 55. 
Timken should be consulted if additional information is needed on any combination of parts or if questions arise about the correct assembly number for a specific application.
The assembly, HM120848 90012, shown in Fig. 2 identifies an assembly consisting of:
2 - HM120848 cones
1 - HM120817XD cup
1 - HM120848XA cone spacer (fitted for normal   internal clearance)
2 - K86890 seal wear rings
2 - K86895 seal assemblies
1 - K86874-90010 backing ring assembly consisting of:   1 - K86874 backing ring   1 - K89716 vent fitting