Choose based on where you clean and the gap size. Slim crevice brushes excel in tight gaps like window tracks, while larger hole-gap or groove brushes handle broader slots. For example, a two-pack with a small head reaches cracks and keyboard corners, whereas a groove and hole-gap duo provides precise cleaning for sliding door tracks. Look at bristle options too: nylon bristles offer durable general cleaning, PP/plastic bristles flex into narrow corners, and blends like dacron/ABS/PP suit mixed gaps. An ergonomic handle can also improve control during long cleaning sessions.