For everyone uninitiated with the Hellerman tool, we had a great thread about mic rigging a while ago here on CB.
Here it is. It's a very specialized tool for adding 1" elastic tubing to
lavalier rigs for theatrical purposes.
H16 is my go to size, and for connectors and such H20 is fine. They will stretch plenty, and you want them to be snug or else they don't hold onto the
wire.