Gamma TNT2 Fat Core XL offers a new take on synthetic gut

Gamma TNT2 Fat Core XL offers a new take on synthetic gut

When a package of sample strings showed up on my doorstep in March, I couldn't wait to try them out.

Then the courts closed down.

Then I was sidelined for 5 weeks with a wrist injury.

After months of waiting, I finally spent some time with Gamma TNT2 Fat Core XL 16. 


Gamma introduced the original TNT Fat Core in 2001. 

The concept of this synthetic gut was that using a larger monofilament core increased the high tenacity filament material by 10%. Gamma’s advanced thermal processing technology, TNT, increases the strength and the dynamic resilience of the string. 

For 2020, Gamma returns with a new, revamped version of the premium synthetic gut string as TNT2 Fat Core XL - a mouthful of a name.

Although the name focuses on the core, be assured that the core is surrounded by wear resistant microfibers and an outer wrap to prevent notching.

Opening the package smelled reminiscent of walking into a tennis shop, and it went into the racket with ease.

Tension and racket setup

53 lbs full bed on the Yonex Ai98 310g

I was coming fresh off of Tecnifibre x-one biphase 18g at 53 lbs. My normal go-to setup is Solinco Tour Bite Soft 18 gauge at 43 lbs.


Power was very controllable from the start when compared to x-1 biphase. If anything, I was expecting more power and was surprised at how reasonable it was in the first session. As the bed started to break in, I was able to keep the ball in the court with no problem on full swing speed groundstrokes. 

The power opened up a few hours in, and was able to do more damage on rallies and got the bigger, heavier bounces that I need to push my opponents back.


I immediately noticed the very low launch angle from Fat Core XL, which dramatically helped control net clearance on slices. This alone was enough to like the string as I struggle with controlling slices on my normal high launch setup. 

For topspin groundies, I was hitting the net cord initially because of the low launch angle, but was able to adjust accordingly.

The string allowed you to make small mistakes and still keep it in in comparison to x-1 biphase where the power would expose any mistake.

Overall, control was predictable and higher than expected for a syn gut.


It has a more classic and flat feel. As a whole, the bed had a stable feel towards the firm side. That firmness could be felt most on slicing where there is lower swing speed, while plenty of stretch and depth to be discovered on big groundies. 

It felt more towards the muted side when compared with a multi, and lacked a bit of feedback. Pocketing was less specific and more distributed throughout the bed.

It was very comfortable, and plenty forgiving on off center hits - just what I needed.


I had to work and adjust my strokes to get spin out of this string. The more flat and linear feel was a fun changeup for me, though. A few hours in when I was more comfortable with it, I was able to generate some heavier bounces as I loosened up my forehand and started to swing bigger.


Durability was better than x-1 biphase and Sensation at the 5 hour mark. There was less fraying than expected. I did not break them and had cut the strings out at the 6 hour mark due to an upcoming match.


I found the string to be higher performing and more enjoyable at the 3 hour mark, and was very happy with the overall consistency and predictability for a full bed. After that point I became more aware of the string movement.

String movement

Around 3 hours I had to start repositioning the mains between points. It did not feel as brittle compared to Sensation.

Tension recommendations

If I tried it again, I would actually reduce it down to 50 lbs to try and unlock more power and spin from it - but I prefer a wild ball. I could see most players easily upping the tension to 55 lbs with no comfort issues at all.



Coming back from a wrist injury isn’t easy, but Fat Core XL provided plenty of comfort and forgiveness while offering a solid foundation of control and predictability. The playing experience opened me up to the world of syn gut strings.

It allowed me to stop worrying about the injury and focus on what matters.

Putting my game back together, and just having fun playing tennis.