Astro Pneumatic Tool PRN516 ONYX Pneumatic Rivet Nut Setting Gun with Quick-Change 1/4" & 5/16" Mandrels 1/4" and 5/16" mandrels included Dial in regulator settings for specific rivet nut sizes and compositions 5/16" rivet nut capacity Forward and reverse actions for quick operation This is a high production tool and mandrel screws are consumable wear items, contact Astro to stock inexpensive mandrel replacements