I do believe you have the models down incorrectly. All 4 inch models are also referred to as "Service". The 5 inch barrel is referred to as the "Tactical".XD9611HCSP0645ACP shows to be 4" Black
XD9611HCSP0645ACP shows to be 4" Black Service model
off the SW website (unless I copied the model #'s down incorrectly)
but the one says "Service" and the other with the same model # does not.