Much like the classic Tortex picks introduced in 1981, these are made from Delrin, which is a trademarked DuPont's take on polyoxymethylene, a type of thermoplastic. Even the familiar turtle design is the same, except here it says “500” on the shell rather than “Tortex”. However, unlike Tortex, which appear to be punched out of a sheet of Delrin, and therefore have square edges, these are cast and have round edges. They are not polished, mind you, so there is a slight nub from the injection molding on the shortest of the three edges. For the majority of people, it will not affect the playability, unless they hold the pick by the tip and strum with the grip (the wide part), like The Edge from U2. In any case, as a perfectionist, I always remove any such witness marks with a 4-way nail file. I have deducted one star for not doing that at the factory, but, considering the cost per pick (of which there is a dozen in the bag, rather than the usual six), it is probably too much to ask. The other attribute setting Delrin 500 apart from Tortex is the texture of the surface. Whereas Tortex picks feel rough (and, some say, “chalky”) to the touch, these are smooth and glossy, which might be a deal-breaker to some players due to their tendency to slip around. Personally, I sweat very little, so it has never been a problem for me. The last thing I will say is that the color is not only pretty, but it also makes these picks a whole lot easier to find on the floor than, say, a transparent yellow Ultex. To someone who is a myopic klutz that constantly drops things, it is a very big deal indeed.