Face it- there's a lot more people with airsoft pulse rifles than their are fully costumed Colonial Marines.
You've dropped £200 on a Snow Wolf/Matrix M41 and scouting e-bay you come up with a 'SCREEN ACCURATE PULSE RIFLE SLING!!!" for £40....A decent 3-point airsoft sling will come in at £20-30 so it's only a bit more, eh- and it looks about right. It arrives in one piece in good time: Instant positive feedback

The fact that it's a £8 GP carrying strap you'll find BOXES of at any militaria show is not known to the buyer.
Sad but true.....
And if you really want to see amazing gouging and carefully wooly worded adverts on Ebay, take a look in the Vietnam War section of Collectables:
~Washed out 1980s £5 US Woodland shirts passed off as £50+ 1960s original ERDLs
~Reproduction stuff of all types being passed off as originals
~1980s ALICE nylon pouches labelled as Vietnam war originals
~And everything and anything even vaguely period being hyped up as "Special Forces LRRPs MACVSOG issue!"
*sigh*
Basically- Taketh thine longest barge-pole and caveat emptor
