These three sanding blocks are designed to work on different surfaces. Each has a height of 20mm. 
 

• the screws in the printer profile are scaled down to 98% of the original size, consider to make them even smaller depending on the resolution. 98% worked for me, first time inserting the screws desired some force. 
• If you print the screws with the .step file, remember to scale the x and y axes to at least 98% of the size of the grinding element.