The most common use for bottles with brush caps is for nail polish or for acetone but it has other uses in labs, where it can be used for all sorts of chemicals which need to be applied in small amounts with a brush. Quality brush cap bottles have brushes that don’t fall apart after just a few uses.
Glass Bottle with Brush Cap:
Glass Bottle with Brush Cap pictured: Techni-Tool Bottle Glass W/ Brush Applicator 1/2 oz.
Glass Bottle with Brush Cap: Micro Trader 10X Clear Empty Glass Nail Posh Bottle 5ml Square Shape Refillable Containers