It was purchased 4 days ago, in the "Inox Full pro" format, with a vertical, metallic Xifias reel and a black 16-17mm rubber.

The next day, I noticed a problem between the trigger and the safety. I returned to the store where I bought it, and after they confirmed the issue, they replaced the gun with another new one. It happens.

Today, I took it with me for the first exploratory test. I loaded it until the second shark: first notch, then the second (!).

First test shot.

Second shot, aiming at a medium-sized fish on a horizontal rock, straight shot, but completely weak... I had the impression (and expectation) that with this gun, I would be able to increase my distance from potential prey - it is more powerful, more accurate, etc. My expectation was not confirmed... the black rubber in the package is clearly weak.

I reload.

Third shot against a large fish that "came to me on a plate," it hit the back and the spear went left, the fish went right. I reload, feeling frustrated, at the first notch. I go for the second one and the rubber breaks in half.

I had read in other comments that when you buy it, you should sand the two slots that hold the rubbers, as the rubbers often break from the edges, remnants of the manufacturing process. I didn't pay much attention to this, thinking that it might have been a coincidence or even if it was true, a brand new rubber would withstand around 20 shots... Any scenario was proven wrong.

In conclusion, anyone interested in buying it should:
1) sand the rubber slots in advance.
2) not rely on the rubber in the package necessarily, but consider using a stronger single rubber or a combination of TWO weaker ones.
3) make sure that the safety is functioning properly.

P.S.: Personally, I am considering the possibility of buying a second spear with threading for tridents, for different approaches - so that I can have a better combo from the gun (and not have to carry two guns with me).
[I can already "hear" and imagine the comments of more experienced fishermen about the above, but this is my own thought, for my own need.]