Granzon Full Armor GPU Water Block and Backplate For ASUS TUF Gaming GeForce RTX 4090 OG (GBN-AS4090TUFOG)

I love the look of it just black metal rather than a bunch of RGB and plastic.
It has kept my GPU temps low even when full immersed in game. Best quality waterblock that I have purchased.

Really glad I gave Bykski a chance. I was in the market for a 4090 OG (note the "OG") waterblock, and there was very limited selection. Another brand I will not name was not able to ship theirs in time so after a bit of digging I found this waterblock.

The block came well-packaged, and included more than enough parts (had a ton of screws leftover, but rather have too many than too little). The instructions are sparse, but at the same time, if you've done this before... the instructions are pretty straightforward. Just be sure to zoom into the image if you have bad eyes like mine to confirm which screws should go where, and what is being covered by thermal pads.

The block itself is very well-built, if anything overengineered to deliver good thermal performance. Beware, the finished product is quite heavy, I have mine in a Lian Li O11D EVO XL with the vertical mount, and I needed a bit of a shim between the vertical mount bracket and a radiator fan underneath it to prevent sag (used some rubber pads, works well enough). In terms of machining/finish, almost everything was fine. There were two screws which don't bite but I might have used the wrong screws, and they didn't seem to compromise contact or thermal performance.

In terms of thermal performance, I have not seen the GPU go above 60C/70C (hotspot) in gaming (BG3, Marvel Midnight Suns, Civ 7, Doom Eternal).

In terms of aesthetics, I wouldn't have minded RGB but the Granzon goes well with my build.

For an unscientific point of reference, I ran the following test for this (unsolicited) review:
Lian Li O11D EVO XL (case closed)
AMD Ryzen 9950X
Asrock Taichi x870e
ASUS TUF 4090 OG
G.SKILL Trident Z5 Neo RGB Series DDR5 RAM 32GB
I have 3 radiators (bottom, top, side) with 3 Noctua NF-F12 fans each.

I ran Furmark (4K) for 1 hour. Ambient temperature was 20C, initial water temperature was 26.8. The pump was set to 100%.

After 1 hour, the fans stabilized at ~1050RPM. Final ambient temperature was 21C, water temperature was 35.4C, GPU temperature peaked at 56C (and was consistently in the 54-56C range) and 66C GPU Hotspot (64-66C range)

Overall, I'm happy with the product. I chose express delivery, and it was delivered with 2 business days as advertised. The product performs well enough. In terms of value, it was quite expensive but watercooling has always been more of a luxury. It's also clear this is a bit of a niche product (the 4090 "OG" variant specifically) so you don't have many options. Overall, satisfied and happy to do business with Bykski.

It is beautiful and HEAVY! I only wish there were better instructions than the simple picture on the website. It would be cool if there was a GPU sag bracket (just because it's so heavy and the socket screws can only do so much) that came with it with the brand name on it or something.

After purchasing the Asus TUF 4090 OC OG I realized the different PCB severely limited water block options. Compared to the competitions over reliance on RGB and plexi this block is extremely sleek and well built. I do wish there were some RGB accents though. This block easily cools the 4090 and it's VRM with temps never hitting north of 55°C during even the most demanding games. Even during benchmarks this card stays cool. I am very impressed with build quality and aesthetics and look forward to more Granzon products in the future!