I have the Denise Interchangeable Crochet
set, and I use it for Tunisian crochet hooks that are longer than 13" quite frequently. The loops come back up onto the main hook without much trouble, and the pointed hook head slips between the loops when it should and doesn't when it shouldn't. Very helpful.
I have no
experience with the Denise knitting set, but have been told that, if you have either interchangeable set, you only need to purchase the "business ends" of what you're missing to have the equivalent of both! I.e., if you have the crochet set already, purchase replacement pairs of knitting-needle ends, and voilá--you'll have both
the Interchangeable Crochet set and the Interchangeable Knitting set!