adidas 4kg Kettlebell - Be All In. adidas Kettlebells are a staple for any fitness regime. Built for both isolated and compound movements, kettlebells develop stamina, strength and muscular endurance; enhancing your overall fitness with dynamic and effective movements. Neoprene coated with a cast iron core - the kettlebell’s knurled handles aid grip with a wide design for both single and double-handed holds. Kettlebells are loved by fitness enthusiasts around the world for a reason - the time-proven classic functional weight broadens your training options for progressive and effective workouts.