(From company literature) Gitzo G1177M Magnesium Center Ball Head. The G1177M Center Ball Head is new to the Gitzo range. It is a perfect match for Series One tripods such as the G1118, G1120, G1126 and carbon fiber G1127 and G1128 models.
G1177M features a precision machined aluminum ball for ultra-smooth operation, along with a single lock for rapid and reliable locking in any position. It weighs under 1lb and can support equipment up to 9 lbs.
The "M" in G1177M stands 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.