Slam Jam x Vibram Rubber Core Boots Chocolate / Black. The iconic powerhouse Slam Jam and Vibram expand their technological and design horizons for the first time. Driven by the desire to find connections between fashion, design, and technology, the two entities collide together to create the Rubber Core boots. The final output is a hybrid shoe made in 5 steps, from the sole to the upper. Compared to the standard shoe-making production, Vibram streamlined the process thermoforming on a 3D last a Vibram StratX rubber sheet to realize a one-step upper. Features include a Vibram StratX Upper, water-resistant material, debossed branding, Vibram Megagrip rubber compound, and Vibram Litebase sole.