We have learned that Arca-Swiss has recently changed the stem configuration of their Z1 Monoball. The stem is now two parts adhered together instead of one solid piece. We are not sure exactly when this change occurred.
Should the adhesive bond between the stem pieces fail, the upper portion of the stem, along with any camera gear that is attached can spin freely and potentially fall completely off.
We feel this is not a trivial safety risk, especially when the head is used in conjunction with our Sidekick, which creates greater twisting forces on this joint.
(To determine if your ball head has a 2-part stem, click on the link below)
Do not use Sidekick with the 2-piece stem version of the Z1.