Hello ZoranM. Be careful with the OG version of the ASUS TUF RTX 4090! The board is significantly larger than the normal OC edition. I can recommend the water cooling block from EK, which is available at this link: 
https://www.ekwb.com/news...The block was actually developed for the RTX 3090, but fits perfectly on the OG edition of the 4090. I have installed it myself and am absolutely happy with it!