Instruction: Evaluate the answerability of a question by analyzing the related document, outputting yes if the document contains information addressing the question, and no otherwise.

Input:
Question: What is the purpose of the built-in safety check valve? How does it work?
Document: The hose connection threads DO NOT CONNECT to ANY standarded R134a refrigerant hose or refrigeration connection, even though the container indicates R 134a systems. This is an incorrectely built can tap valve assembley for R 134a systems. DO NOT BUY!! !
very very good and  so perfect or quickly or easily work and heavy duty and  no leak to  the valve
You cannot get a better valve than this. Solid brass and built to last. Tight connections / Does not leak. You have to tighten it down a little harder, but it seals better. I attached this valve to my old but good hose. Now I have a great charging hose again. Don't waste your money on those crappy AC charge line hoses with the cheap plastic connectors. If your valve leaks, replace it with this Mastercool valve.
After waiting for a week for my new gauges to do some very important work on a demanding schedule. ... it turns out the whom ever posted this adapter for these gauges did not know  what the hell he/she was talking about or had a freakened clue. what a jerk. Please do not order this adapter..mastercool 85510 r134a can tap valve-screw-on model for $12.11. Please don't waste ur time, it does not work ,,,period.
Worked fine, few times, then blockage. Apparently/looks like, there is a little ball check valve in the male fitting?? Anyhow - clogged or broke, nothing will pass thru. This happened when I had just tapped a full can so now I'm out the cost of the valve and a can of freon.
Very good quality and smooth operation. It just feels well built by the way it works when you turn the handle. Nice piece !
While this can tap is very well made, it won't fit those small cans of R134A that you find in auto parts stores. It doesn't help if it's built well if the product description is misleading. I got a refund on this product and bought the Mountain 8401 Top Style Metal Can Tap, which fit my small refrigerant cans as well as my Harbor Freight gauge set.
fine deal. this is not quite as flimsy as the other that are out on the market. mine seem to work. hope it holds up
This item would have rated higher if i hadn't had to buy more fitting to make it work on new style cans
Took a lot of fiddling with this to get it to work on CA cans of R134a. Not sure that it's a real good fit.
Answer: yes