An adjustable length post for a bicycle comprises first and second slidably coupled supports, the second support comprising an interior cavity defined by an interior surface, the interior surface having a portion recessed from a surrounding surface; and a collet coupled to or integrated into the first support, the collet comprising a body positioned at least partially within the interior cavity of the second support; a locking member pivotally or slidably coupled to the body, the locking member repositionable between a locked configuration and an unlocked configuration, wherein, in the locked configuration, the locking member protrudes laterally from the body an amount sufficient to engage the recessed portion of the interior surface of the second support, and, in the unlocked configuration, the locking member does not protrude laterally from the body or does not protrude an amount sufficient to engage the recessed portion of the interior surface of the second support.