The CM51 was first released in 1953. The U model is fitted with a special version of the 934 omni-cardio capsule. It is attached to the body by a clever swinging system and can pivot at 360 degrees. Different capsules can be easily switched. This mike has an attractive vintage shape. The downside is that it produces a bit more self noise in comparison to more recent microphones so I use these for drum ambiance and in this context, they do a great job.