Superior Wooden Test Tube Support, 12-Place Entomology & Zoology_Entomology Supplies Wall-mounted Mason's hygrometer with two

Wall-mounted Mason's hygrometer with two identical dual-scale thermometers — one dry and one kept wet via a water reservoir — calculating relative humidity from their paired reading difference

the medium-strength option for classroom investigations into magnetic poles and field-line geometry

110 ohms at 1-ohm resolution

supplying a duplicate-value option for paired-bench experiments on capacitor energy storage

Superior Wooden Test Tube Support, 12-Place Entomology & Zoology_Entomology Supplies Wall-mounted Mason's hygrometer with twoTwelve place hardwood test tube rack combining ten 19 mm holes and two 25 mm holes with twelve draining pins for mixed size storage and inverted drying on the bench.