I've just bought one of these Lunaforce L4E Chipset Waterblocks. Of the pictures I have seen of it unassembled it looks quite unrestrictive but we will see. Its got 12mm barbs (1/2" ish). I'm fed up with the noise of the fan so if it doesn't affect the other temps too much I will be well pleased. The other screw taps directly into the bottom


