Save for our illustrious leader's (Steve) knowledge of same, the use of so-called Foster fittings is much scarier than most airgunners realize. The main problem with them is the fact there is no industry standard. In fact, some are so sloppily made, undersized males can blow out of oversized female fittings with predicable results!
Steve Archer, Steve Dampier (Airgun Guild) and yours truly, have campaigned this issue for several years. Unfortunately, manufacturers of airguns and the suppliers of the fittings seemingly don't care. Making matters worse, the materials used, along with the design of the latching ramps and the number of latching balls, makes apparently snug fitting ones (male-to-female) a bit dangerous.
Again, the issue is complex and not centered on one individual factor. Perhaps that is one of the reasons nothing has been done with respect to a standard design.
Making matters worse, there is no airgun standards committee. What's needed is a SAAMI (Sporting Arms and Ammunition Manufacturers’ Institute) for the airgun sport. That too is lacking. I've gone on record with this thought: Sooner or later, the Fed will get involved, and we all will lose to some idiotic standard.
For more information, Steve (Archer) has several articles here on H.A.M. covering the details. Perhaps if enough airgunners complain to the powers-that-be, something will eventually be done.
Alan Applegate