This is a set of four Dubro fuel line plugs (two small, two large). These are also known as fuel dots.
Features: The plastic plug has a ball that extends 1/4 into the fuel line for a positive seal
Requires: Installing into the end of a fuel line
Note: The small size fits 1/16 (1.5mm) and 3/32 (2.3mm) size tubing and the large size fits 1/8 (3mm) and 5/32 (4mm) size tubing.