Stainless Steel Hook/Eye Turnbuckles

A4-AISI 316 stainless steel hook/eye turnbuckle

These are also known as tensioner, turn buckles, straining screws, adjusters or barrel strainers and are avaiable in 4mm, 5mm, 6mm, 8mm, 10mm and 12mm diameters 

One end is right handed and the opposite end is left handed, you create tension by simply rotating the turnbuckle center body