Flat Definer

Sonia G Flat Definer Brush is described as a "mini shader, smudger, and flattened pencil brush" that is supposed to be "stable at the tip" for "neat and even application." It's very thin without being floppy, and it is slightly thicker at the base as it narrows toward the edge of the brush, which is rounded overall. For someone with a smaller eye shape or who does really detailed work, this brush could be quite useful.

It is a fairly small brush, definitely in the vein of a brow or liner brush, but in a more classic shader shape. In some ways, it reminded me of a stubby take on a lip brush, as it was denser and a bit firmer like a lip brush. Depending on the angle, the ferrule was sometimes noticeable, but it was less noticeable compared to Builder One, which felt thicker in the hand overall (which isn't surprising given the difference in handle styles). It functioned similarly to Builder One but achieved more precision when used to apply product to the inner tearduct or lid. I found it useful for getting a shimmery highlighter right under my brow bone without blowing out the shimmer too brush, so it was quite precise.

The edge was comfortable along the lower lash line and never felt sharp when held horizontally against it, but it still had good movement. The rounded edge did take some getting used to for me as a liner brush, and it performed best for me when I used shorter strokes to apply, and as marketed, it delivered a softer line of product. 

For smudging out eyeshadow or eyeliner, I felt a pencil brush worked better and more efficiently for that purpose, though this brush could do it in a pinch (the Soft Shader was better within the set for smudging).  This brush did work well for picking up product and precisely laying it down over smaller areas, like adding eyeshadow over an eyeliner (and not wanting it to be really smudged or diffused).

• It is made out of brown-dyed, saikoho goat hair.
• 148mm length, 8mm hair length, 7.7x4mm ferrule width