Lifting Slings/Lifting Sling/Lifting Belt/Lifting Strap are usually made of either polyester or nylon materials.
There are two kinds of slings which are widely-used.They are flat Webbing Sling and Round Sling.
Flat webbing sling has loops on both ends,and its length ranges from 1 meter to even 50 meters.
Round sling is like a circle,it does not have any loop.
Both webbing sling and round sling has strong strength,or we call it lifting capacity,normally ranges from 1Ton to 15Ton.
And there are 4:1,5:1,6:1,7:1 even 8:1 safety factors.The higher the safety factor is,the stronger the sling is.