Characterized by its unique and durable construction, the Sigma 77mm WR Ceramic Protector Filter is a clear filter designed to protect the front of the lens against impacts, scratches, and other elements. Developed from a transparent glass ceramic substrate, this filter combines a high transmission value of 99.76% with greater hardness than chemically strengthened glass and more flexibility than sapphire crystal glass. The result is a shock and scratch-resistant construction to withstand a variety of impacts during shooting. Additionally, a water-repellent coating has also been applied to resist water droplets and fingerprints, as well as static electricity that attracts dust or other particles. Designed for use in challenging conditions, the unique design of the WR Ceramic Protector Filter helps maintain the inherent image quality of the lens while offering a high degree of protection.nn- Clear protective filter that shields the front element of the lens from a variety of impacts and scratches without affecting image quality.nn- Transparent glass ceramic is a highly durable substrate that has greater hardness than chemically strengthened glass and more flexibility than sapphire crystal glass.nn- The unique construction has a Vickers hardness index of 700HV, making it resistant to scratches and shocks. This hardness also reduces the likelihood of scratches or chipping that could lead to filter breakage.nn- Rather than hardening only the surface structure, transparent glass ceramic involves a heat treatment process that precipitates microcrystals of a mineral called spinel to achieve consistent and uniform strength across the entire filter surface. This strength also allows the filter design to be remarkably thin and light.nn- A water-repellent (WR) coating has been applied which, in addition to preventing water and oil from adhering to the filter surface, also helps minimize ghosting and reflections. This coating reflects 0.24% of light, giving an overall transmission value of 99.76%.nn- The WR coating also serves as an antistatic coating, which helps repel dust or other particles that might cling to the filter surface.nn- The included hard acrylic case protects the filter when not in use and has been designed to prevent accidental and unwanted opening.