This are just right for the DIY advanced hobbyist. To obtain perfect welds , all you need to do is make sure both ends of the copper pipe are clean, use coarse steel wool, and use the flue paste, then fit your fitting and apply heat with a portable propane torch until the ring of solder shows at the edges of the fitting, then let it cool (do not pour water) and you have a durable weld.
Someone told me that the Yorkshire weld contains lead ... well, you'll have to research that one.
The fittings come in a great variety of shapes and have ends for taps and joints for galvanized iron, if you want to hook up to galvanized.