DNA Paints aluminium mixing sticks, 3 different types available with popular DNA mixing ratios:

Orange Mixing Stick 5:1:1 and 60/40% (1.5:1)
Blue Mixing Stick 4:1 & 2:1
Green Mixing Stick 3:1 & 1:1

Solvent proof, easy-to-read, easy-to-clean and the perfect size for 1300ml mixing cups.