Review on Leak-Proof Screw Cap Glass Test Tubes Set of 6, 85mm Length with 5 ml Marking, Perfect for Aquarium Water Tests - Tililly Concepts by Crystal Robinson

Two of these broke from repeated cap tightening. The minimal force needed was enough to seal them. Compared to the tubes that come with API kits, the 5mL mark is NOT accurate. I have a 5ml syringe that I use to pump water from a reservoir. When filling the API tubes, they are filled precisely to the line. Everything is different when filling these tubes as they are all different.