This upgrade uses 400mm rods and a 12x6in aluminum plate to extend the build volume of the Printrbot Simple to ~140x290mm. The bolts attaching the metal plate to the upgrade are countersunk so they sit flush, increasing printing area to near full. Parts that it requires are listed below:

15x 20mm M3 Bolt
4x 25mm Countersink M3 Bolt
4x M3 Nuts
GT2 Timing Belt
2 Zipties
4 Springs from Clicky Pens

The 4 counter sink bolts are used for bed leveling in conjunction with the springs from the clicky pen. The final 20mm M3 bolt is used to trigger the X end stop. The rest is pretty self explanatory when looking at the pictures.