Kuryakyn 6309 ISO Contoured Left Side Throttle Boss The addition of a throttle boss can make the difference between a quick trip and a cross country adventure. Simple to install and are easily adjustable to suit your needs. Updated styling combined with a larger surface area and pad. Designed for more comfort than the original while still easing hand and forearm fatigue. Fits Kuryakyn ISO-Grips, ISO-Flame Grips and Transformer Grips.