Just reviewing the Omer detachable handle guns as I now own all three versions picked up brand new for bargain basement, no name band gun money. The design was rather ambitious as they relied on using nothing but the inner barrel tubing from existing pneumatic speargun production. Most brand name spearguns are made by subcontractors, they are not in-house products, although the design parameters are no doubt drawn up by the company if they want something different.
My guess is Omer sketched out the guns, the Airbalete comes first, and having done their sums figured they would not be making enough money if they made them in Italy. They could either abandon the project or find a cheaper alternative. Given the long delay between when the Airbalete was announced and actually ready for sale I suspect this was because they handballed the job to Taiwan and possibly asked them to make the guns as cheap as possible, but without going overboard. Given a free hand the Taiwanese factory began to look at cutting corners and that is how the guns turned out.
I expect that the Airbalete production line was troubled by the need for a unique tank for each gun size as it is not like you can slice a length of tubing to the correct length as hydroformed barrels are made to size. No doubt looking for a way around this the Sporasub One Air evolution meant they could sell the same gun and just chop the triple hollow tube extrusion off to the required length. Another cost saving was these tanks are painted, probably powder coated, they ain't anodized and they have a rough texture as they are not entirely smooth. To provide a point of difference they also used a vacuum barrel muzzle using the STC system, that was a mistake as these use front tied spears, you can go back over half a century when those were used before.
The last and best gun of the set is the Omer Air XII, it has a tubular tank of greater diameter and has dispensed with pretending to be a band gun based on the Omer Cayman handle design.
Another fundamental flaw is the spiky bumps on the piston nose, they allow a gap to be seen through the relief valve ports. If you want to smash up plastic shock absorber anvils then you need a meat tenderiser mallet, Omer put it on the nose off the plastic piston! An admission of "we done wrong" is the spare shock absorber anvil supplied with the guns in later years. What to do about it is take the piston out and flatten it off ensuring that at rest the piston seals don't poke out the front of the end of the inner barrel tube. This last boo boo is handy for letting formerly trapped water out of the space in front of the piston with the gun discharged, but not at the expense of smashing shock absorbers and possibly the piston itself.
By the time I bought the Airbalete, which was the last of the three. nearly everything had gone, so I had to settle for this brown mimetic version rather than the black or the green mimetic. Mimetic finish looks nice, but only the white handle will find your gun again if you drop it cocked and ready to shoot.
Because the guns were sold off to get rid of them many came with the reels and extra handgrips of a more ergonomic type for free, the Airbalete even scored a shaft holder for different sized shafts no less that clipped on front and rear and which is next to useless. Carry a spare shaft sure, but ones of different diameters?