Pentax 61804 UP 10x21 Binoculars are part of the Pentax U Series of durable and compact binoculars, ideal for a range of uses from the theater to the field. The U Series puts Pentax clarity and quality within reach at a reasonable price. These compact porro-prism models feature a dual-axis, single body design with synchronized eyepiece adjustment, and aspherical lens elements to provide exceptional edge-to-edge sharpness. Pentax U Series Features: Fully-Multi-Coated Optics - Fully-multi-coated optics assure maximum light transmission resulting in high quality viewing. Every surface of every element is fully coated minimizing internal glare and flare and giving a bright clear view. Apherical Lens Elements - Aspherical lens elements, critical in compact binoculars, give you edge-to-edge sharpness, assuring that items on the edge of your field of view are just as sharp as those in the center. Unique Uni-body Design - Unique Uni-body design enhances durability by locking objective lenses in a single housing and synchronizing the eyepiece movement, minimizing moving parts and assuring the binoculars will function clearly and properly for years to come.