Same here, I thought it was the tube thickness, not another tube inside, in that case 22mm is too wide IMO. How about 13mm while incorporating a jet into the 'innertube'?
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PS, I would'nt of put restrictive barbs onto it though. I'd have used 13mm (inner diametre) copper pipe in conjunction with 13mm (inner diametre) silicon tubing...
The outlet is in a good position to run a northbridge block in series as well...
PPS, with regards to the size: Is this block for a Pentium4 CPU?...