RockSlide Nickel plated brass Guitar Slide small size: 17.5mm x 47.5mm. Small Rock Slides are the sports car of the slide world, very light weight and extremely fast. Nickel plated-brass Rock Slides are a great combination of tone and string feel. They are slippery like glass, but have the weight and long sustain of brass. Unlike the polished brass slides, they remain slippery for a very long time.