In 2004, the MoCo started using plastic oil tanks. There were two factory installed versions, 04-06 (62888-04 ) and 07-09 (62888-04A).
The 04-09 oil tank versions share the same basic setups as the oil tank and electrical junction box (that is vulnerable to moisture). ¹⁾
The EFI bikes use up more space in the junction box, having an additional relay and more fuses?).

Late 2009, they came out with an upgrade version (62888-04B) with a 10 PSI pressure relief valve in the top of the tank, right side.
The -04B tank fits 2004-2009 Sportsters and also has a less restrictive vent tube configuration inside the tank.

04-09 Oil Tank Upgrade (62888-04B) 2)