Prym Ergo Yoga Cable Needle

Prym Ergonomic needles all have a wonderful "bulb" at the end that they call a "hook tip," that hooks the yarn from falling off as you work it, and these cable needles are genius! They have an additional flexible metal middle section covered with rubber so you can bend it to any shape you like, while the rubber helps grip your stitches so they don't fall off. 

Two sizes available:

The small size comes in a set of 2, 8" long and US 6 diameter (4.0 mm)

The large size is a single needle, 10" long, and 7.0 mm, technically a US 10.75 (not an often used size un the US)

My recommendation- as longe as the cable needle is smaller than the needle you are knitting with, you will be fine. The small set will work for anything US 6 or larger, the large size may feel more comfortable if you are always knitting with super bulky yarn and sizes US 11 or larger.