The original Gridfinity base by Pey fits in a 7x12 grid into Ikea Alex drawers. In total the original design measured 297mm x 525mm.
However, my Alex drawers measure 295mm x 523mm. There are lots of comments about the original's fitment, being too tight.
I removed 2mm from the width and 2mm from the depth to fit my Alex drawers perfectly. No sanding or cutting required. Simples.
The author remixed this model.
Reduced width and length by 2mm