Instax Mini 99 Filter Adapter

I have always wanted to take long exposure photos during the daytime with instant film but it's always been super awkward trying to hold an ND filter up to the camera without shaking or bumping it and causing an issue with the final result so I decided to design an adapter for a variable ND filter I already had. This adapter is designed to fit a K&F Concept ND2-400 77mm thread Variable ND Filter (note to anyone who wants to print this: the THREADING on the filter is 77mm but that is NOT the diameter of the filter, the ACTUAL DIAMETER of the filter is 85mm) however I could imagine this filter adapter would work just fine with a plethora of filters as long as they can fit within its confines. The filter adapter is designed with teeth to hold the filter in place so it doesn't fall out when pointed downward or shaken and it fits snuggly on the Instax Mini 99 by friction fit. The friction fit on this adapter is solid, I spent a whole day going back and forth across the river taking