I repaired a hole I could get almost my whole thumb in my aux tank aft of the rear axle and have been using it for almost two years now with no problem. It is call Pro Seal as far as I know you can’t buy it on the civilian side, but if you don’t find and thing else let me know I can get you some. I am a Blackhawk crew chief and we use it to seal just about everything on army aircraft. shian.huggler@us.army.mil