Made from 18-8 stainless steel, these flange nuts have good chemical resistance. The flange distributes pressure where the nut meets the material surface, eliminating the need for a separate washer. Height includes the flange. Skip the washer?these metric stainless steel nuts have a flange that does the same job, spreading pressure across its surface for a strong hold. They're also called collar nuts. By leaving out the washer, they save assembly time, which adds up on parts that have multiple bolts. On the other hand, they may not fit into tight spots since they have a wider profile than standard nuts. All are 18-8 stainless steel, which is nearly as strong as steel and stands up to outdoor, washdown, and other corrosive environments without rusting.