This is a collection of different spacers to make a conversion to singlespeed for mountain bikes. You can use a mtb cassete and use the cog with the desired teeth count and use the threaded cap. I suggest you use measure the position of the cog and calculate the combinations of the different sizes of spacers. A solidworks model is provided so you can also set the size of the spacer you want. I suggest you leave approximately 1mm sticking out of the hub body so the threaded cap can provide enough clamping force. Also, you should print a test spacer and adjust the scale. 101% scale provides enough clearance and makes it easier to mount.