This is a part for the Image .12 engine from Traxxas. On the later engines this is a replacement part. On the earlier engines this is an upgrade over the plastic wrist pads.
This Package Includes:
(3) G-pin retainers - These are the retainers that holds the piston pin (AKA wrist pin) from coming loose inside the cylinder. These fit into the groove in the sides of the piston.
Comments:
Traxxas suggests that you install these inside of a box to prevent losing the spring (they easily spring loose when installing).