The Onfinity Base, Drop Arm and Attachment is a very convenient way to do hose/tube control from the rear on a Onefinity, known to work on the X50 with a Z20. 

First an exploded view of everything you about to perform to properly install this. 

First we'll start by installing the square nut in the slot on the underside of the Onefinity Base

Set that aside, and we'll grab the (2) 3d printed parts that form the Drop Arm and use the two M5x30 screws to secure it together.

Next we'll grab our previously set aside Onefinity Base and align it to the top of the Drop arm. 

Using the M5x14 Screws you'll attach the Onefinity Base to the Drop arm. 

Next slip the square nut into the bottom of the Arm and put your attachment on there snapping in with the magnets. 

Screwing in the remaining screws to the front of the attachment, and on the sides of the attachment in the drop arm. 

Use the remaining screws to secure the drop arm to your Onefinity