PF is a good source of certain chemicals not sold by others. They are a source for Glycin. I have bought paminophenol HCl from them. Other companies that I buy from are www.chemistrystore.com and www.techcheminc.com. The Chemistry Store sells inorganic chemicals such as sodium sulfite, sodium thiosulfate, sodium carbonate, etc. They do not sell developing agents. I buy these from Tech Chem Inc.