Adidas retro Plug tech?

[irishbaz]

Can anyone explain what was the tech behind the adidas Plug tech? I know its 1884 retro but what was the purpose of plugs? they look like golf tees stuck into the midsole!

 

[bigpunoy]

If I remember right, they were of different densities so it was like changing the softness/stiffness of your shoe. I remember there was a full page ad for the retros in like Slam back in the day.