National Hardware's 5/16" Black Interlocking Spring Snap with eyelet allows quick attachments of all types of material and equipment. Steel body and spring construction provide maximum durability. Designed to install and remove quickly and repeatedly. For quick repeated attachments in a wide variety of applications. Use with chain of equal or lower working load limit. Medium Duty Rating with 300 lbs. Safe Working Load, always follow safe working load (SWL) limits included on packaging. National Hardware's Lifespan Limited Lifetime Warranty.