As soon as I made this linear slide: http://www.thingiverse.com/thing:5625I wanted to make a modification.There are a couple of challenges with that first design. First, the very large piece is very hard to print and get totally flat. It wants to warp. Second, the design requires a fixed size separation of the two smooth rods. That's going to be fine for certain loads and directions, and not for others.So, this thing is a piece of a reinterpretation of that design. This one piece simply captures a 608 bearing, and provides a nice stable piece that can be threaded onto a 5/16" threaded rod.This thing, in combination with a couple of these other things: http://www.thingiverse.com/thing:5678Would give you what you need to make a linear slide of any size (length and separation) for an endoskeletal bot. 1) Print a couple of these when creating a linear slide. 2) Press fit 608 bearings into the large opening. 3) Thread the thing onto 5/16" rod, with other components 4) Add other components to your design to complete your linear slide 5) Rejoice!