Dumbbells offer a number of advantages over other types of weightlifting equipment. They're relatively easy to store and versatile enough to perform almost any exercise, and they challenge your muscles not just to lift weight but also to stabilize it. Dumbbells work to your advantage, however, only if you can keep them under control, so the best dumbbell handles will be sized and shaped to fit your hands, with some sort of texturing to help you maintain a solid grip.
Sometimes Size Matters
Like standard barbells, dumbbell handles are typically about 1 inch of diameter. You'll find handles of up to about 2 inches in diameter for use with heavier weights. Adapters can help you transform a standard dumbbell handle into a thick one. If you're just casually lifting weights, however, your priority should be finding a dumbbell that feels comfortable in your hand -- and a 1-inch diameter does that for many people.
Textured for Your Safety
The cross-hatch texturing on some metal dumbbell handles is called knurling. It helps you maintain a firm grip, even when your hands are slick with sweat. Vinyl dumbbells won't have knurling, but the vinyl itself acts as a non-slip surface. If you frequently lift weights with knurled handles, you may develop matching calluses. Weightlifting gloves are the best way to protect your hands against this.