Timing Belt GT2, Printrbot Simple Tension Block 2.1mm

Tension Block for use in Printrbot simple GT2 belt modification by iamjonlawrence
http://www.thingiverse.com/thing:194686
and
http://www.thingiverse.com/thing:194586
The belt and pulleys i bought from amazon.com
http://www.amazon.com/gp/product/B00GNWBUW6/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
must be a little thicker than the one used by iamjonlawrence, when i reflect mine over on to itself to lock it into the block it cannot pass into the narrower side of the tension block. So i modified the tension block for my belt, making the opening 2.1mm.
Note: my printer makes inside dimensions smaller than the model on the stl so if you measure the opening in the model it's 2.7mm, but on my simple it prints out at 2.1mm in the actual object.