McMaster-Carr offers most of the variations. The type I purchased has some kind of filler for wear resistance .. doesn't specify what. They also offer the AF, and fiber reinforced varieties.
Their description: "Because these naturally slippery, wear-resistant rods and discs resist expanding when exposed to heat and moisture, they can be easily machined to close tolerances. They are a good choice for parts that require precision, such as gears, bushings, and bearings. DelrinŽ acetal resin is also known as acetal homopolymer; it is stronger and stiffer than acetal copolymer."
They also offer Acetal Copolymer as a "economic alternative" to the Acetal Homopolymer .. and various types and fillers for that too
I opted for one of the more affordable versions of the homopolymer Delrin, instead of the PTFE filled Delrin ... which is in the area of $70 / foot in the size I needed.
Yes, quite the rabbit hole when you start looking at plastics.