Characterised by its exceptionally durable construction, the Sigma 72mm WR Ceramic Protective 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 a hardness superior to chemically strengthened glass and greater 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 repel 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 Protective 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 superior hardness to 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 impacts. This hardness also reduces the likelihood of scratches or chips 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 minimise ghosting and flare. 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 rigid acrylic case protects the filter when not in use and has been designed to prevent accidental and unwanted opening.