I was looking around on the internet for a ph pen that is top quality. Found the hydro centre phone number. Phoned up the hydro centre and asked the staff about which ph tester would you use and explained that ive seen some cheap ones that aint good and wanted a top quality one that would last for years. Got recommended the bluelab ph pen, Which has just arrived about 5 mins ago about to test my ph levels in my hydroponic system. Bluelab ph pen comes with care instructions, Which is very helpful. Staff knows knoweldge about hydroponics and what you will need if you are planning to grow from seed. Very great service, top quality product head into shop, phone call or order through website