For four decades, Fox Head, Inc. has been a global leader in the action sports industry producing dynamic designs. The Fox Head logo is recognized as a brand synonymous with quality and innovation, while remaining true to MX. Replacement LP1 D3O® shoulder insert. One size fits all. Sold individually. D3O is a long-chain polymer with off-shoots. The intelligent molecules move freely among themselves and, in the case of a collision, they move past the off-shoots together and spread the force over a large area. The D3O protectors are very soft, flexible and thin. And, they adapt to fit the body.