A side note: At one point it was cheaper to buy an entire self-centering dowel jig from Harbor-Freight and use the drill bushings for other jigs, than it was to purchase the bushings alone.
The Harbor-Freight jig looks OK, and it might be OK once you are able to adjust the thing to be in the actual center. But I struggled to do that and quit. Some of those self-centering jigs have integrated the bushing into the jig so those are not removable (Dowel-It, for example). Others have two removable and two integrated. The best have all four removable as that allows you to use one setup to drill 4 same-sized holes.
There are some “bushings” out there that are simply accurately sized steel tubing, and are not hardened as a true bushing should be. Those are cheaper and far less durable, especially considering that with each use of the drill bit you will be essentially teeming the I..D. oversized. By appearance, that is the type that is shown in the videos.
Also note that plating does not “throw” well inside tubing. So any plated bushing is likely to be bare or nearly bare in the interior of the barrel. Of all the metals for plating, nickel “throws” best but is very soft and wears out quickly. Black oxide + oil is probably the best, Treat with WD-40 for storage.
Infinity Tools produces one of the best of this type with all bushings being removable and from-the-factory centering accuracy. At about $70.00, it is also one of the more expensive ones (and the one I always use). The bushings appear to be of a universal size and seem to be interchangeable between brands.
The image below from INFINITY TOOLS. The blue tape is a poor-man’s depth clamp. The best (and easiest to use) clamps are of the type that squeezes the two halves together (cheap ones on Amazon). The ones that use a single set screw for clamping require careful placement of the screw and often does not sit level. I would avoid those. The image below shows the better type to use. The pictured one was likely plated prior to assembly and the interior of the clamp has full plating coverage.