Utility articles

Can someone explain to me the alternative dumbbells in this photo taken from the J & J site?

It is just a matter of preference. I think. I stick with the normal dumbbells. The square ones with 2 bars seem easy to pick up for smaller dogs, same with the triangle ones.

They're all allowed in AKC though? I've never seen them.

Yes they are all allowed in AKC.

I think in AKC you can use ANYTHING as articles as long as they are all identical and you have a leather and a metal set. Someone I knew used Ball jar lid rings, another used crushed popcans!

That is correct, anything can be used as long as they are all identical to each other. You can use whatever you want metal and leather wise.