The stainless steel shackles we use on Harken® blocks are available separately. Harken forged stainless steel shackles are polished to a high luster and are stamped with the screw pin diameter. The breaking strengths shown are derived from weights supported by 80% of the length of the shackle pin, similar to the length spanned by an appropriate block's headpost.
Bow shackles are best for multidirectional loads. Their large interior opening allows plenty of articulation especially when attached to a round bail.