Hornady Modified Case 300 AAC/Whisper 107507. A special fine thread is used to attach them to the gauges ensuring that they remain perfectly square for precise alignment in the chamber of your firearm. Second the neck of the case is made perfectly round and opened slightly to allow a standard diameter bullet to slip into the case mouth effortlessly but concentrically to ensure the most precise results possible. NOTE: Dial Caliper and OAL Gauge not included. Image may not be representative of color or style. Specifications for Hornady Modified Case 300 AAC/Whisper: Manufacturer: Hornady Caliber: .300 Whisper .300 AAC Blackout Package Contents: Hornady Modified Case 300 AAC/Whisper Hornady 107507: Modified Case 300 AAC/Whisper