Vivaldi yarn

I needle help determining a yarn weight for Vivaldi yarn.

The yarn description says “needle size 4”. Would this mean 4mm, or does it mean US size 4 (which is 3.5mm)? Or, could it even be that they’re saying it’s a UK size needle, size 4 (US size 10/6mm)?

It gives a gauge of 19 sts x 26 rows = 4"/10cm, so stitchwise, does that put it in the DK category or the sportweight category (or somewhere else)?

http://yarndex.com/yarn.cfm?yarn_id=449

Yarndex says it’s worsted, and the 19 st/4 inches tells me that makes sense.

Thank you!!! I always forget about yarndex! :muah: