In the game the E11 is a type of ROTJ with extended stock (also known as E11B)
http://starwars.wiki...b_blaster_rifle
But before we had the game skins, the E11 looks more like the dressed ESB (no greebles) than the ANH that has the counter/power cylinders etc... So for a closer alternative, the ESB style was kept in.
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As for the Holster. When the CRL were originally made, people asked if they could have an holster (because they wanted to be able to holster their E11 sometime at troops/events). I used the only reference for a TKC having a holster, which is the Sideshow. This was ask about before: ------- Since the TKC did have a reference (Sideshow) it could fall under the EI. It should also read "Holster may be omitted from this costume." I will fix that.
As for the HWT holster, the same thing (people asked if they could have an holster) Since the HWT does not have any reference of having a holster, it was not allowed for EI, only basic approval.