First of all, this was designed to help me replace the OEM belts on my H2D's.  I have over 4,000 hours on each of them, and the belts are starting to fail (one broke).  I looked into the Belt Design (see photos attached), and the OEM belts (Black color) are an aftermarket 9mm x 1.5mm pitch belt.  They are NOT Gates Power Grip 1.5GT 9mm RF Belts (Brown color).  Voron printers recommend and use the Gates PowerGrip belts, so I decided to use these Power Grip Belts instead of Bambu's OEM belts.  I am not an expert on belts, and this guide is for cutting the belts to 1824mm (for the H2D, Other models have different sized belts).  For me, the Power Grip Belts work equally well, I see no difference in quality, speed, noise, etc.  They may not last any longer, but I decided it wouldn't hurt to try them. 

the Power Grip Belts appear to have more linear fibers, and are shown in Brown.  the OEM belts from Bambu are black in color.

The issue I found was cutting the belts to the exact size needed (1,824mm).  The old belts were stretched out, and they couldn't be used to accurately to cut the New Gates Belts. Additionally, you will want to glue your NEW belts to your OLD belts and then pull it through the printer, Something you can't do if the Old Belt is pulled out first for measuring.  You can use a NEW OEM belt as a measuring device, but I thought this would be fun to try and design this.

Word of advice, change your belts before they break!   

In the photos included, you will see a new OEM Bambu belt laying in the Cutting Jig, and the length is exactly the same size as the ends of the printed guides.

You will want to print eight of these, and they snap together like a kids Wooden Train Set.  The belt lays in the grooves perfectly (if they don't, you either have a stretched out belt, or the wrong pitch).