We sell only HD5 Propane which is the consumer grade. HD5 means it contains a minimum of 90%propane and a maximum of 5% propylene. Producers also produce an industrial grade HD10 which allows up to 10% propylene and can cause some sticking and gumming problems in an engine. Lastly, there are some off-spec products, and with these, who knows what you’ll end up getting. We, however, proudly sell only HD5 consumer grade propane. If you are a home owner be sure that you are getting HD5 so that you do not develop problems with your tanks, cylinders, engines or appliances.