The 3/8 fitting doesn't hold up under pressure and keeps blowing off of the quill. Gave these quills a try because they appeared high quality and were about half the price of where we have previously been sourcing injection quills. Fortunately, I still had a few of my old injection quills in stock and was able to finish the job for my client.
My application: I'm running an 80psi (max) demand pump for an injection application into a ~55psi irrigation line. I figured there were enough margins there that the quill would definitely hold up. I have 3/8" tubing running from the pump to the chemical injection quill and it keeps blowing off of the injection quill. The longest I managed to keep it on there was about 5 minutes until it blew off and proceeded to soak the surrounding area with my product.