Reference 70™ (REF 70™) are ISO grade 5.8 elevator bolts with a concave head and four lugs on the underside to help prevent rotation when tightening. The REF 70™ bolt, when coupled with the special oval washer, is ideal for steel elevator buckets in heavy-duty industrial applications on larger diameter pulleys over 50 cm in diameter. Because of this domed area under the bolt head, these bolts are not recommended for flat back plastic buckets, especially on thinner belts.