OMC Evinrude Johnson Washer DLR

The " Washer DLR" OEM drain/fill plug washer, specifically the one that replaces part number 311598. It's a rubber or stainless stell flat washer used to seal the drain/fill plug on the lower unit of these outboard.

Here's a more detailed breakdown: 

Function

The DLR washer creates a watertight seal between the drain/fill plug and the lower unit housing, preventing water leakage when the plug is tightened 

Material

It can be made of rubber or stainless steel, depending on the specific application and replacement part

OEM

It's a replacement part manufactured by OMC, Evinrude, Or Johnson ( often Sierra or other reputable brands) to match the original specifications.