Upgrades over original model:
There are 2 version you can print:
Snug Fit - width of bit slot is 6.45mm, the bit can still easily be removed and is my preferred sizing
Loose fit - width of the bit slot is 6.50mm, you would print this if your printer is maybe printing a little on the big side
Print this version and the original and i guarantee (or your money back) that this version if far superior.