here is the 1/2 pipe squashed to make a jet.
one is 1/2 pipe and the other as a 1/2 coupler.
the coupler gives a wider jet as it is a couple of mm bigger.
here with not jet
here with the 1/2 pipe
and the coupler
the only problem is there not wide enough to cover a p4 heat spreader which is 30mm these are only 22 for the pipe and 25 for the coupler.