DC PWR PLUG CONVERTER, CONVERTS 2.1MM TO 1.7MM

This converter has about a 4mm outside diameter which was too large for what I wanted it for. The other 2.1mm to 1.7mm converter that Allectronics sells, the DCA-4, has a smaller outside diameter, maybe 3.5mm or so, which worked for my use.

I think it is a better design than the type which has intervening wires between the 2 fittings. Although I have both, I like the feel of a tight fit between the 2 sides. It then acts as a single plug, rather than a union of 2 parts.