Plump dk is a pretty standard doubleknit or light worsted weight yarn. We have used it for straight double knit projects as well as projects specifying an aran weight yarn and found it works well for both. Any needle size from 3.75mm to 4.5mm is great.
Ballband Tension (gauge):
Using a 4mm needle over stocking stitch: 22 sts to 10cm and 30 rows.