This is a small device which converts any NATO40 connector into a pushfit. 
 
This has multiple benfits, the first is that it improves the safety, now you can quickly remove any tube by pulling. Stopping the need to unscrew anything.
 
Second this allows quick and fast changing of any attachments. Super helpful for a dom to change between what is connected.
 
As these are friction fit parts over time it will slowly get easier. to pull apart. Therefore, to start with the two bits may not completely fit together, this is by design so that as the two parts sand each other, with will come together more and more prolonging the life.