Yup...original DeWalt was double.
I called my mate up and asked why I had a tangled birds nest...he just kept saying it's easy just wind up the spools...eventually we worked out they'd made it a load of rubbish and mine wasn't the same as his..
Thankfully the STIHL spool fits and is an excellent design....the 2.4mm is a lot better for what I need (edging me allotment plot). It mows down everything.
If you soak the line in water it makes it more pliable so it lasts longer & doesn't snap off at the eye! Yes I know it sounds rubbish, I thought that until I tried it and it does work. I keep a few pre-cut lengths of line in a container of water ready for use.