This is a replacement straight crankarm (no offset) that is the same as what is shipped with the BBS01 & BBS02 drive units. You must specify a side L or R when ordering. The Right is the drive side and the Left is the non-drive side. You must use the right side crankarm for the correct side of the bike<br><br>Be aware when mounting pedals that the left side pedal is reverse threaded so you tighten it backwards (counterclockwise)..Drive side is normal, clockwise to install it.