What is Retractable Brush

Answer 1

 

A retractable paint brush consists of two parts: a short handle with bristles and another bit that covers the bristles to protect them. To use the brush you remove this and push it onto the end of the handle to make it longer.

Retractable brushes are perfect for traveling as they take up less space and the brush's hairs are protected. They're available in different sizes, the same as 'normal' brushes.