What are the differences between MuscleDriver USA Kettlebells?

Gray Series Version 2 Kettlebells - Single cast, cast-iron, textured finish with 1.5 inch smooth handle. Gray hammertone paint similar to what would be on hex dumbbells found at any local gym. Perfect for those who want a little texture on the handle and base of the kettlebell. Removeable rubber boot on bottom.

Pro Series Competition Kettlebells - are a quality kettlebell at an incredible price. The Pro Series Competition Kettlebells are single cast and have a wide smooth thick 1.5-inch diameter handle for ideal use and comfort. All Pro Series Competition Kettlebells are the same size and meet competition requirements.

Fitness Series Kettlebells - Single cast, cast-iron with red vinyl coating on the base of the kettlebell. Black painted handle is 1.5 inch thick and is a smooth throughout. Vinyl coating is perfecting for protecting floors and prevent chipping. Perfect for physical therapist, gyms and personal trainers.