The A03928 Unloader with the 11MM seat is the A01726 Unloader Valve with the updated 11MM Seat and O-Ring.
The A03928 Unloader Replacement Kit comes with the complete Unloader Assembly and the Replacement Unloader Seat for the replacement of the 1 piece unloaders D29539, 16355, 18139 and D29540 that were used in the oil-free strap series pumps.
This A03928 Unloader Replacement Kit Will Not Work !! as a replacement unloader valve for the 16355 Unloader that was used for the Oil Lubricated pumps that were used on the DeVilbiss and Ex-Cell pressure washers including the PK16330, PK16331, D29105, PK18219, PK18339 or other oil lubricated pumps that used the 1 piece unloader assembly.
If you have an Oil Lubricated pump do not order this A03928 Kit thinking it will repair your pump.... It Will Not Fit the Oil Lubricated Pumps and no refunds will be given for parts that has been used or attempted to be installed.