Accuracy Solutions 7in Picatinny Rail Black 17 Slots. 934 inches/176 mm long .433 inch/11 mm thick. It has 17 Slots. It has a total of five (5) through holes sized to take 10-32 screws. The diameter of the counterbores are .488 inch/12.4 mm which is sufficiently large to take 1/4-20 or 1/4-28 button Head Hex screws. To use these rails with 1/4 screws simply enlarge the diameter of the through holes. The five holes are distributed 1.576 inch/40 mm apart from center to center of holes. This rail will mount to the bottom ofF.A.S.T. chassis fore-ends. Look through the pictures to see a technical drawing of this rail. Specifications for Accuracy Solutions 7in Picatinny Rail: Manufacturer: Accuracy Solutions Color: Black Finish: Type III Hardcoat Anodizing Gun Rail: Picatinny Length: 7 in Additional Features: 17 Slots Package Contents: Accuracy Solutions 7in Picatinny Rail Accuracy Solutions AS-2026-40: 7in Picatinny Rail Black 17 Slots