/ 4.5mm 
.
Not used as yet, looks like a reasonable bit of kit, not a bad price and arrived promptly.
Given 5 stars, would be less if it refuses to go down the hole, It's not that scary down the hole but you never know with a new piece of kit.
I'll report back if the hole monster chases it off.
Visited in person to get a better viewing of the hand winch. The lads were most helpful and accomodating and offered after sales help if needed. Would definitely recommend.
Good quality item, easy to install and operate and does exactly what we wanted it to do. Fast delivery and email correspondence.
Great set of rollers! Have been using for last 12 months and no issues. Well made and about to buy a second set. Used for pulling concentric cables, 250m 150kg 5 days a week!