I've got an RV8 from a Range Rover / P6 / MGV8 (I call it 'composite'

One of the 2 pipes at the front that run from the water pump to the inlet manifold has a pin hole in it - but the amount of water it can shift when up to pressure is surprising

As there 2 hoses were never replaced when I built the engine, I don't actually know what the ID of the rubber is?
I'm looking to replace them with silicone hoses, and 16mm springs to mind?
Cheers
Tom.