Micro Mesh Pad Holder

I'm using Micro Mesh mini sanding pads (regular and MX) extensively.
So I designed myself a pad-holder that would

• keep them sorted
• allow them to dry (wet sanding)
• tell me the coarseness
• have symbols to roughly compare the coarsness of regular and MX pads
• interlock to extens this sorting system
• add a module for bottles of Mr Surfacer while I'm at it anyway

I printed these on an Ultimaker II. Every module needs about 7 hours using the Cura medium quality default settings.