Terrible. I bought some calibration fluid with this pen to make sure it's accurate. Although it was "factory calibrated for immediate use," it differed by 200 ppm from the calibration fluid. Whenever I tried to calibrate it, it always gave me an error message. According to the instructions, "Err" messages indicate internal damage or "the meter cannot calibrate" but do not provide advice on how to fix it. The $12 ppm tester I've used for years is more accurate than this $30 bunch of hot junk. Don't believe this bizarre disappointment.
OUBEL 30V/10A Adjustable Lab Power Supply With LED Display, Alligator Clips, And US Power Cord - Ideal Switching Regulated DC Power Supply For Bench Applications
11 Review
Contact lenses Bausch & Lomb Soflens Daily Disposable, 90 pcs., R 8.6, D -7
55 Review
LifeStraw Go Water Filter Bottle: The Ultimate 2-Stage Integrated Filter Straw for Hiking Adventures
10 Review
14" Notebook ASUS Vivobook Pro 14 OLED K3400PA-KP112W 2560x1600, Intel Core i5 11300H 3.1 GHz, RAM 8 GB, DDR4, SSD 512 GB, Intel Iris Xe Graphics, Windows 11 Home, 90NB0UY3-M02070, cool silver
20 Review
Get Your All-Purpose Cleaning Solution With Bealee'S 24 Oz Plastic Spray Bottles - 2 Pack
16 Review
ULAB Scientific 1000Ml Borosilicate Glass Beaker With Printed Graduation - Durable And Accurate For Lab Use (UBG1005)
12 Review
Get 24 Pack Of 4 Oz. Amber Boston Round Glass Bottles With Droppers From GBO GLASSBOTTLEOUTLET.COM
11 Review
3Pcs 500Ml CVNDKN Wash Bottles W/ Scale -16 Oz: Plastic Safety Lab Squeeze Bottle
13 Review