Our newest dampener is for the 500 size helicopter. This dampener is our newest design and incorporates a unique composition of materials allowing for a smoother progressive dampening. This is a hard dampener. This material has a very long life. We have one test pilot who has well over 100 flights and three crashes on a set of dampeners with little signs of wear. Do not use oil based grease on KBDD dampeners. Use soap and water or Lithium based grease if desired.