Following discussion on UKRM regarding the GPA strapless helmet, I've decided it's easier to put-up some pix rather than trying to describe it.
OK, a general view showing the moulded visor and front ventilators. The white
patches are reflective.
Introducing the "red button". Also note no BSI sticker but it is Gold ACU.
Close-up of the red button and the Quick Safety Release, this is the same on
both sides.
When the buttons are pressed the front hinges down...
this also unlocks the rear, allowing it to open...
... far enough to get your head inside, without the usual struggle.
The only weakness in the design is the visor. This includes moulded "poppers",
or rather moulded tabs that form the female section, clipping onto metal studs
on the helmet. The tiny tabs break-off so the visor comes away. This visor
was modified with a Dremal and metal poppers fitted. The angles not quite
right, spoiling the action.
The snug fit round the neck keeps drafts out but makes it awkward to fit an
intercom headset. Here the headset was fitted between the inner and outer
shells and the cable lead out through a hole. Neat but it probably doesn't do
much for the shell strength.
Overall this was the most comfortable (once I'd eased the slight forehead pressure) and quietest helmet I've had in over thirty years. The only reasons I had to replace it were the visor problem, visors are also impossible to get in the UK, so I picked them up in France and Germany, and the helmet was getting a bit old, though it doesn't show.