(From company literature) Gitzo G0077M Magnesium Center Ball Head. The G1077M is the lowest profile head in the range. Lightweight yet robust, it weighs under 0.5 lbs and can support equipment up to 5.5 lbs.
The G1077M features a precision machined aluminum ball for ultra-smooth operation, along with a single lock for rapid and reliable locking in any position.
The "M" in G1077M is for "Magnesium". Gitzo were the first to introduce Magnesium heads to the photographic industry. Magnesium offers the advantage of being up to 20% lighter than regular photographic heads.