Determine which collet size you need by its position on the pole
The small red collet fits onto the aluminum slider tube of both the Pro-Lok 3-section and Alumiglass 3-section extension poles.
How to Replace the Chuck & Collet Locking Mechanism
NOTE: Even though this video shows a fiberglass handle and aluminum slider, the procedure for two aluminum tubes is the same. Just be a bit more cautious of the rough aluminum and file it down if it has metal shards after cutting.
The old chuck and collet locking mechanism will need to be removed from the extension pole. Some customers have used a hacksaw or dremal tool in order to cut the old mechanism off. Please be careful of the aluminum tubing underneath. Once the old one is off, the red collet will go on first. You will dab some epoxy at the end of the aluminum section about an inch from the cut off. Then slide the red collet over the epoxy, it will be a tight fit. Tap it on a flat surface and let it dry. Once the red collet is all set, you can now insert the slider and put the black chuck in place by threading it down onto the collet.
Just what I needed.