1/4-28 .165-.260 Large Flange Ribbed Nutsert Steel / THREAD DIRECTION: RIGHT-HAND HEAD STYLE: D13 FLAT HEAD DIAMETER: 0.500 INCHES NOMINAL HEAD HEIGHT: 0.037 INCHES MAXIMUM NUT STYLE: A23 BLIND RIVET W/SPLINED SHANK NUT DIAMETER: 0.390 INCHES MAXIMUM NUT LENGTH: 0.720 INCHES NOMINAL SHANK END TYPE: OPEN THREAD SERIES: UNF THREAD QUANTITY PER INCH: 28 NOMINAL THREAD SIZE: 0.250 INCHES MATERIAL: STEEL OVERALL SURFACE TREATMENT: ZINC OVERALL AND DICHROMATE