Men's Georgia Boot Mud Dog Work Boots These pull-on Muddog Comfort Core work boots are durable and comfortable. Made with only the toughest of materials, such as SPR leather. Compared to traditional leather, SPR leather is roughly 3 times as strong and resists abrasions 2.5 times as well. It stands up to many chemicals and acids due to a rare blend of proprietary materials. The comfortable boot has a Comfort Core insole which features a heel plug for shock absorption and airflow channels promote breathing. A fiberglass shank provides arch support and steady footing.