This is a print designed to hold all the components of the API Freshwater Master Test Kit. There are two additional slots for any other API bottles you might have, I'm using mine for the GH & KH test.

The fit on the bottle holders is deliberately a little tight so they don't fall out when in storage. I've included a test fit print so you can make sure your printer gets the tolerances right. If its too tight, just scale the model up 1% or 2% :)