Vreg (MOSFET) are the chips that controls the power of your CPU and the colder they are, the more stable is the power supply for your CPU, which means you can overclock it even more.
They develop much warmth and the normal passive heatpipe cooling solutions (with or without additional fan) is in most cases not good enough when you first start to overclock. This is due to - among other things - that the contact between them and the heatsink are usually not particularly good, so there may be much to gain by switching to a better and more efficient cooling solution.
This water block is made specifically for mosfet on Nvidia 790i motherboard.
Model name (manufacturer's number):
Material Top: Plexi
Material base: 99.99% electrolyzed copper
Interior Design: Multi Pass
Thread: 2 pcs 1/8 "BSPP (G1 / 8)
Nvidia 790i reference design motherboard
1 pcs cool head
NOTE: The product is supplied without fittings.
Fittings with 1/8" BSPP (G1/8) thread is suitable for this product.