Satin Charcoal Japanese Sen (ASCS), Garnet Japanese Sen Burst (AGJB), Satin Black Japanese Sen Burst (ASBJ) & Indigo Japanese Sen Burst (AIJB). There is one more important consideration. The spike is separated from the rest of the spur by rubber, which absorbs the impact without transferring it to the spike itself, allowing the bass drum shell to vibrate and resonate more freely.