The Harken 072 Stamped Stainless Steel Shackles are designed for low loads and can be used with most Harken Small Boat Blocks. For heavier loads, opt for forged and high-resistance shackles instead. These 5mm Micro Shackles weigh 8g (.29 oz) and have a shackle pin size of 5mm (3/16"). They have a maximum working load of 567kg (1250 lbs) and a breaking load of 1134kg (2500 lbs).