Original Unicorn Horn Brush - The bristle width on these synthetic hair brushes is about 6-7mm. (First image and second image on the left.)
Le Petite Unicorn Horn Brush - The bristle width on these synthetic hair brushes is about 5.5-6.5 mm. It's just a tad smaller than the Original Unicorn Horn brushes and has 1/3 less bristles. (First image and second image in the middle, third image on left.)
Baby Unicorn Horn Brush - The bristle width on these synthetic hair brushes match that of the Le Petite Unicorn Horn Brush. These come with longer handles and a rounded brush shape. (All images on the right.)
One of Each - This includes one Original, one Le Petite, and one Baby Unicorn Horn Brush
TIP: These can be used as a cleanup brush for nails, eyebrow brush, eyeliner brush, etc. Of course this is as long as you dedicate that brush to that purpose.
To extend the life of your brush be sure to clean it with acetone between uses. Do not leave the brush sitting in acetone even for short periods of time. Acetone Antidote may extend the life of the brush due to the conditioning elements of the additive.
Thanks to @nailbastion for the beautiful photos!