PISTON AS 4678051 - Caterpillar

Engines In All ApplicationsThe Reference Article announced the use of a nylon seal with lockwire for sealing critical engine components such as governors, fuel systems, timing access bolts, etc. The second chart lists the four colors of seals and the use for which each color is intended. Now, an optional black seal is available only to NACD (North American Commercial Division) dealers.
This black seal is available only from the seal supplier and is for use only by NACD dealers. It is intended for certain NACD customers who choose to do their own fuel system work or make performance adjustments. The black seal will NOT have an imprinted code, as do the other three parts service seals, and is for use at the dealer's option.
Refer to the second chart in the Reference Article and add this black seal. This makes a total of five seals in the chart, four of which are available for parts service to NACD dealers. The yellow factory-installed seal is not available for service replacement.
All NACD dealers are still requested to order the appropriate color seal(s) directly from the supplier. Do NOT order the Caterpillar part number; this is available only to dealers other than NACD dealers. The Reference Article tells NACD dealers how to order their parts service seals and lists the supplier's address. Orders by NACD dealers to Caterpillar will be blocked by the computer and not accepted.