This tri-fold case is designed to hold a set of interchangeable circular needles--the needle tips and cables as well as DPNs and fixed circulars plus a large zippered pocket in the back to hold loose accessories and tools that might otherwise get lost. I am not brave enough to use DPNs myself and only have one 5" set. The two side panels are 6" wide so they hold mine perfectly fine. But those of you with the longer DPNs (like 7") might want to increase the overall width. An easier option would be to sew narrow pockets in the center panel for longer DPNs. Overall, this has been designed to suit the needles and tools I have, so I highly suggest you read the document thoroughly first to see if want to make any changes or modifications.
View, download or print the directions here.