6. What are the differences between the audio filters? And how to change it?

The flagship FH7S comes standard with three interchangeable audio filters. Each audio filter has its own damping and filter density, allowing you to choose between three different sound signatures.
Red tube——boosts bass, achieves deeper insertion in ear canals when working with bi-flange or triple-flange ear tips
White tube——presents detailed treble with high resolution
Green tube——presents great treble details in every music note
*The white audio filter comes pre-installed. The other filters are on the included storage sheet.