1. Some people call them "wedge clamps", or "strain hangers". I've only used them from one manufacturer. The name is "Blackburn".
2. Some advice on cutting quadraplex....don't use your side cutters. There is a hard drawn steel strand in the messenger, and unless you are using 2000 series Kleins, it will ruin your pliers.
3. I agree with Sparky on 310.20.
4. You'll also notice that the insulated conductors have "ribs" on them. The "ribs" are for identification purposes.
The Watt Doctor