The bottle caps are blue's innovative system of nine interchangeable capsules, each offering the recordist a different tonal characteristic and pickup pattern. from airy highs to larger-than-life lows, the bottle caps capture anything from vocals to bass, wind instruments to horns — and everything in between with a level of detail and clarity found in only the most expensive and rare vintage classics. the bottle caps work with blue's bottle, bottle rocket stage two, and bottle rocket stage one mics, or any microphone with a foundation for interchangeable capsules. each capsule in the series is numbered from b0 to b8, and each has their own unique sound. b8 is the best choice if only using one capsule - crystal clear sound quality and excellent detail for a wide range of recording applications. suggested applications: male & female lead vocals, electric & acoustic guitars, drums, drum overheads, percussion, piano, horns and strings.