Engl Hardtailer Trem Block System

A great product in concept but poorly executed.
The brass fine tuning screw is very loose and constantly moves as you play, so when the time comes to engage the hardtailer it will no longer be in the correct position and your guitar will go out of tune. I also do not recommend using the tremolo at all while the hardtailer is engaged, as this also causes the screw to move a lot and make the guitar go out of tune as you're playing. On the contrary, the sliding mechanism is extremely stiff and unpleasant to use. The pull mechanism to engage the hardtailer is uncomfrotable and will hurt your fingers with the amount of force required to move the stiff sliding mechanism.
The hardtailer is advertised to have "no rattling noises" however there is a lot of loud rattling noise between the brass screw and the tremolo block whenever you pick hard, there is also an annoying clunking noise of the tremolo banging against the screw when bending strings or using the tremolo (which again, I don't recommend as the guitar will go out of tune).
The only good experience I've had with the hardtailer is using it to completely block the tremolo under high spring tension so the brass screw can't move and the tremolo can't move to create the loud rattling noises caused by the hardtailer, but this isn't what the product was designed for.
I recommend seeking alternate solutions for temporarily blocking your tremolo.

That product is great.
I had some doubts before ordering.

I thought It could negatively impact the sound in a blocked position.
As it turns out, the only slight problem is that if you bend too hard, there will be a noticeable sound (tremolo will clash against the blocker when you release a bend, when you bend, tension will increase and Floyd will elevate against the blocker).
However, you can solve this problem by slightly readjusting the blocker once in a while. I have noticed this problem ONLY when changing the tuning of my guitar without readjusting the blocker.

The benefit of blocking tremolo and dropping my guitar with a d-tuna-like product outweighs my cons.

Hardtailer can sit in the way of springs, so be aware of that too.

Install was a bit nerve wrecking, but worth it.

The screw does not move on my unit, maybe Engl has added thread locker such as Loctite 222. I have not checked.

It fits under the trem springs in my case. However, this is going to depend on the thickness of your sustain block. You can try sliding a 3mm hex wrench, under the springs of your guitar, to check.

Overall I am very happy with this product, but I wish 2 things were better.
1. It is stiff to lock and unlock
2. The provided screws are magnetic, which is acceptable, but not desirable or necessary in this application.

Compared to a Tremol-no, this is the better product. More dependable, does not unlock itself.