Small retractable fiberglass brush. Merry-Lee tested these in her studio and was delighted with the function and form. As they wear out, you simply twist the knob to lengthen. Super convenient!

4 1/2 inches, in a pen-like casing.

For a review of this product go to:

https://merryleerae.thinkific.com/courses/tool-time

Or https://youtu.be/4Lra4eN65VM