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The growing popularity of kettle bells, the primitive-looking bowling-balls-with-handles that deliver a great all-body workout, has given rise to similar products with more flexibility. Available now are weight-changeable kettle bells that can be customized to new fitness levels, for different family members or even during a workout — so you don’t have to own more than one. Below, find four innovative ways to throw your weight around.

1) Plastic fantastic

U-Fill-It Kettlebell:

Hollow 2-pound plastic kettle that can be filled with water (12 pounds), sand (18 pounds) or metal shot (49 pounds).

Likes:

Very user-friendly. The smooth, hard, rounded plastic and thick handle feel great in your hands. It glides smoothly across your skin at all times. It fills easily through a 2 1/2-inch-wide port on the bottom; the threaded plug is locked tight with a dedicated four-pronged wrench. Quite durable and leak-free when tightened properly, and it did not crack after dropping it during juggling and hand-to-hand drills.

Dislikes:

Switching between weights during the workout, as done easily with the Weider, would be a messy hassle, requiring dumping the water and pouring in a bag of sand or shot. Beware misplacing the wrench, because hand-tightening the plug could be leaky.

Price:

$49. 866-89-PUNCH;

theartofstrength.com

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2) Sandbagging it

SandBells:

Not a kettle bell but a soft, handleless, nylon-coated neoprene sack filled with sand or shot that you grab at the edges and use for kettle bell movements — and more.

Likes:

Strenuously works your hands and fingertips. The precarious grip and shifting sand add a new level of difficulty to “easy” movements, such as swings. It encourages the creation of challenging exercises, such as swinging overhead, 10-foot throws or downward ground slams. I did 20 throws with the 30-pounder and was gasping for breath. House-friendly, the tough but soft bag won’t rip and will not dent hardwood floors. Available in weights from 2 to 50 pounds. It’s adjustable — you can pour sand in or out, altering weight and grip. (Optional funnel is $2.) It can be emptied for travel.

Dislikes:

Might be too much work for some. The hand fatigue shortens the exercise duration. No DVD is included, although several SandBell workouts are found on YouTube.

Price:

10-pounder (empty $16.99; filled $18.69); 20-pounder ($39.99; $43.99); 30-pounder ($59.99; $65.99). 888-460-0628;

hyperwear.com

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3) BYOP (Bring your own plates)

Kettlestack:

Handled device with minimalist frame that allows you to bolt on your own weight plates. Includes a standard Allen wrench, a center axle to hold the weights and a variety of male/female bolts.

Likes:

It works just like a regular kettle bell, which can grow with your fitness as you add weight plates. I cannibalized some old dumbbells and built a 32 1/2-pound kettle bell out of four 5-pound plates and five 2 1/2-pounders. It looked ugly and primitive, but my rounded plates didn’t feel uncomfortable on presses, like the Weider. Weights above 85 pounds will require wider axles ($12).

Dislikes:

Sharp-edged plates would not feel good against your skin. Changing weights during a workout is slow compared with the Weider, but simple and fast enough to adjust for another user.

Price:

$55. 866-423-0922;

kettlestack.com

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4) Quick-change swinger

Weider Adjustable PowerBell:

Multipart adjustable kettle bell made of a handle/frame and six dedicated weight plates that can be removed or added in seconds.

Likes:

It works perfectly. The design is handsome and efficient; just slide a spring-loaded handle on the top and release the desired number of plates. It’s safe because the handle can’t be moved unintentionally. Two models are available: the 40-pound max, with a 10-pound handle/frame and a half-dozen 5-pound weights, and the 20-pound max, with a 5-pound handle and 2 1/2-pound plates. Both come with a workout DVD and a healthful-eating guide.

Dislikes:

It works fine for standard swings and dead lifts, but overhead presses are a no-go; the cylindrical (not spherical) shape, horizontal plate stacking and sharp plastic top edge uncomfortably scrapes your forearm when flipping it over to the back of your hand. It rattles a bit, and the 1-inch-wide handle is thinner and less comfortable than that of a normal kettle bell.

Price:

$249.99 (40-pound); $99 (20-pound). 888-308-9617;

weiderfitness.com

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