Slightly-Better 3/8" Extension Holders

These are the first of several widgets that I'm creating for better organization on Ernst® magnetic socket rails: they are a robust socket extension holder with a redesigned interior profile that offers significantly better retention for 3/8"-drive extensions than is offered by the factory extension-holding-clip-thingies...so if you have a set of Ernst® magnetic socket rails and some prone-to-wandering-and-wobbling extensions, you might want to print one or seven of these. Salient points are as follows:

• Single- and double-clip units will be available; look for updates on the latter. At current, I just have the single-clip uploaded.
• Length is a full 1.000", which is twice the length of the factory clip and capable of holding any extension up to 12" long with just one holder. The factory option is a great design, but due to a shorter length and a slightly different cross-section, a single unit simply cannot securely hold an extension by itself; you need two for every extension.
• Two interior diameters are available: the smaller is designed to work with extension shaft diameters between .450" and .480", and the larger works with shafts .480" and up. The smaller offers good retention on standard-duty 3/8" extensions, and the larger one works well for impact extensions. Note: I will be also be uploading a semi-universal variant that holds almost as well as these do; it should accommodate almost any 3/8" extension shaft diameter at the expense of a slight reduction in holding power. If in doubt, use the universal one when it becomes available.
• As stated, these fit the Ernst® magnetic socket rails; they probably fits the non-magnetic ones as well, but since I don't have the non-magnetic models I can't say for sure. If you don't have either of those socket rails...well, this extension holder is likely to be almost entirely useless to you, but you could probably employ it for something if you tried hard enough. In a pinch it could be a bizarre micro-sculpture, a closure for a half-empty bag of Doritos™, a clamp of questionable utility, or even the worse tweezers of all time; be creative.
• Due to the increased length of the base I've added a second set of detent teeth to the interior of the rail interface; these work about as well as the factory detent teeth, which is a phrase that here means "they're really hard to get on the rail the first time, but then they wear down a bit and we start to wonder why they're designed this way in the first place, because they don't ever work as well as they did that first time." I may change the detents in the future because I'm not 100% happy with them, but since they work as well as the factory system I'm letting them out as-is.
• Polished extensions may still slide inside these clips, even if they lock into place firmly: that's just the nature of polished cylinders. If that kind of thing bothers you, don't apologize for it; I'm also that pedantic, so I get where you're coming from.

As usual, I've printed these in the same not-really-matte black PETG that I use for everything else, and they seem to do just fine; other filament choices are available, but I can't speak to their properties. Please let me know if you try these in a variant material; I'd appreciate hearing how they turn out.

Lastly: I'll be adding a set for 1/2"-drive stuff in the future; I'll post that link here when I have them uploaded.

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