RONSTAN BLOCKS Ronstan shackles are strong, reliable and economical. Several basic types are available in a range of sizes for all applications Materials: Grade 316 Stainless Steel bodies and pins. 630 TWISTED SHACKLE 5/16 D(in) | L(in) | W(in) | (UDL)BL(lbs) | (PL)BL(lbs) | WEIGHT(oz) | SHACKLE PIN NO. | 5/16 | 17/8 | 5/8 | 7920 | 5940 | 2.3 | RF34 | |