I've gotten quite a few over the years and I always make a mixture of Rhizotonic and water and drip several drops on the helmet many times during a 24 hour period. I do that until the hemet takes a hike. I also germ in Rhiz and water in shot glasses. Depth isn't always the stubborn helmet cause.one of these had helmet head. my fault i didnt bury deep enuff and it fell in upside down and no correction was made. other one is strong