1/2" to 3/8" NPT reducer

[ROUSTABOUT]

You can you water pipe fittings for high pressure lines, however you will potentially have increased failures. High pressure fittings have tighter tolerances, and better quality control. The biggest issue is liability. Lawyers can get pretty excited about using low pressure fittings for high pressure applications. If its your own stuff then feel free to, the risk of using a water pipe fitting on a top link or little 8' disc is minimal. However personally I would not use it on a loader or something that does overhead lifting. If your doing work for a business, I would not use anything that was not rated for the pressure due to liability, the cost of a fitting is much less than the cost of losing a lawsuit.

Who put it on there? I didn't put it on there. Never seen that before in my life. I don't know how that got there.

I will answer exactly the way my government has taught me to. I have no recollection of that (remember that one?).