Contains Rock Bottom Standard vertical mount arm, guide, spacers, and hardware all designed specifically to keep your chain on through the harshest conditions. With tight clearances there is no room for the chain to disengage from the chainring apart from sucking in large debris or impacts to the guide. It is only for bikes with a standard chain-line that runs straight from the cassette to the front chainring (NOT for bikes with high pivot idler pulleys). Slap Guide technology pushes your chain more on center the harder you ride. It works on rigid frames all the way to full downhill suspension.