The HYDRA® MARCK-15 HYDRA is the most advanced Modular AR-15 on the planet! This Weapon System can adapt to multiple calibers without the use of any tools in just under two minutes per caliber. That’s right! One Weapon…Multiple Calibers!!! The idea of quickly changing calibers on one weapon’s platform almost doesn’t sound possible. At HYDRA WEAPONRY, the possibilities are endless and with so many calibers at your fingertips to choose from! The HYDRA® Conversion Packages will give you the option to pick and choose your favorite caliber for your Hydra. (less)