Im taking care of 3 spas, we have ICO Spa devices, which need to calibrate every 6 months. Set with 4x20ml of liquids and original plastic stand costs 31€ and 4x 500ml bottles from original manufacturer of liquids costed 124€. I made stronger version of plastic stand for repeated use.

Printed on MK3s

PETG

0,3 layer height

3 walls

4 top/bottom 

15% adaptive cubic infill

Prepared also bgcode for MK4s