Pentax K-Mount HD DA 21mm f/3.2 ED AL 21-21mm Fixed Lens for Pentax KAF Cameras Wide-angle equivalent to 31.5mm in the 35mm format Ultra-thin, pancake design, landscapes, buildings, interior rooms High-grade multi-layer HD (High Definition) Coating.Diaphragm Automatic, 7 blades (rounded) Unique super-compact design in two colors