Push In repair collet and o-ring 3/8" pn 7209574
Repair part for Sears RO ( reverse osmosis ) connections, but similar to any "quick connect" / "john guest" Fitting ( push in to lock, pull out to remove ).
See how to remove tubing,How to Use Standard and Quick Connect Fittings - Video
NOTE: Some RO Units ( especially older models ) us 1/4" tubing for most or all the connections.
And it's the O.D. ( outer diameter ) of the tubing that determines if you have 1/4" or 3/8" tubing or fittings.
For more on how Fittings are Identified,
see:Fittings Measurements Different Then Expected ( 1/4 and 3/8 fittings )
To remove the old "Collet",
you must pull it out with needle nose pliers.And excessive force may be required.
Then you will have access to the o-ring underneath the Collet ( in the hole )."Fish" it out ( small tool of any type ). Installation is the reverse. Put o-ring into the "hole", and then PRESS the new Collet into the hole. It will "lock" into place.