Ok just checked MV and someone is/has making/made a big booboo.
On Peeron it says that the thin chin strap 193a came on nearly every set containing a blue helmet with the only set containing the thick chin strap 193b being the XT 5 and Droid.
I don't have the XT 5 but every blue spaceman I have has the 193b helmet and MUST have come in all those sets that say came with the 193a.
Unless I lost or had stolen every blue dude from my collection and somebody secretly replaced them with 193b helmeted men without my knowledge.
I'd inform Peeron and Bricklink if I wasn't so damned lazy.