TNT Airsoft APS-X Hop-Up System GHK M4 Gas Blowback Rifle Retrofit Kit (Length: 455mm)

"Easy to install and it just works, no fuss

"This is the best hop-up unit upgrade out there that you can get for your GHK M4, hands down. Thanks to its unique bucking and outer barrel designed especially for this hop-up unit, you get fantastic grouping and consistency. You can feel the outstanding quality of the inner barrel because it is built like a tank. The unit itself is purely metal and it is very easy to adjust, it follows the design of the stock GHK hop-up unit but 1000% better in quality, strict hop adjustments and accuracy.

I purchased the 370mm that is a perfect fit for my GHK FSP. It is a rather tight fit but it is designed to be like that. This is a pure drop in upgrade and that requires no modifications whatsoever. Once you've taken it out of the box, it is ready to drop in. No need to assemble it together.

With this upgrade, I noticed better grouping and consistency in my shots. The wheel adjustment is pin-point accurate. Once you've dialed it in your hop, your gun is set and ready to go. It is a smooth rotation wheel and it doesn't feel janky like the stock one. As you are dialing in your hop and once you have found that sweet spot, keep it like that, it is set and ready to go. Small 1-2mm adjustments to the left or right, it'll mess up that sweet spot.

Pros:
- Built like a tank. Fantastic quality and QC. Perfect tight fit in GHK chamber.
- Great grouping and consistency. (Tested at 150 feet)
- Tight fitment.

Cons:
- When installing it, I found no cons or any displease.

For $125, it is absolutely worth it. I was sketchy at first but I'm real glad that I got it.