3mm the diffrence is designed for the diffrent style of track you would be running on.
1mm
The .22 bullet is smaller than the 9mm in size, (about 6mm) and is lighter in weight.
6 mm = 0.6 cm, or 6 cm = 60 mm, so the difference is 10x.
Airsoft bbs are made up of plastic and are 6mm in diameter and are .24 cal, BBs however are metal and are .177 cal (4.5mm)
2.4 mm All kidding aside: the 3.5mm lens has a wider angle than the 6mm one. This means that in a picture, you will see a larger area with the 3.5mm lens, but with the 6mm lens you'd see more (sharper) detail.
dear me,,, 6mm, sigh!
6mm is equal to a 2 gauge.
4mm-6mm in inches = -2
6mm is thicker than 2mm.
6mm = 6/1 mm.
A flexible cord is a flexible cable having a conductor cross section less than =<6mm squared providing a high degree of flexibility for non fixed wiring systems
Well there are 4 6mm beads in an 1", so there would be 64 6mm beads in 16".