The RapidPress coupler and slip coupler are used for joining tubes and fittings from sizes 15mm to 108mm.
The RapidPress coupler is used to join tube together when you can move the tubes apart freely. They have a small indentation around the fitting that ensures the tube stops at the correct insertion depth.
On the other hand The RapidPress slip coupler does not have the indentation around the fitting. This allows the coupler to be slid completely over the tube. This allows you to join tube in an application where the tube can’t be moved apart before inserting it. However it is extra important to remember to witness mark the tube being pressed with a slip coupler. This is because there is no indication of how far the tube has been inserted from either end.