The relatively open design and the large 1/2" copper connectors used for barbs make the R Type a fairly low flow resistance block. I would guess that the 1/2" copper barbs are the major reason for the increased flow rate. It is also clear that the R-Type block does quite a bit better than the Lumpy Channel block at less than 1.25 GPM. This is consistent with the thicker base used on the R-Type.



Link: Procooling