It may be obvious somewhere on the product page that the meter does not come with anything that actually measures dissolved oxygen. The meter should only be in the title, not in the fine print. Probes are sold separately.
π PH 1-14 Extensive Storage Testing Monitoring: Optimize Your Storage with Precise pH Level Monitoring
6 Review
Portable digital multimeter with sound continuity and thermocouple (electric tester) LTX DT-838
7 Review
Efficiently Test Your Antifreeze And Battery Acid With A 3-In-1 Refractometer
18 Review
TDS water quality tester - TDS water hardness meter (portable digital salt meter for water analysis)
9 Review