This is the product I bought:
https://www.ebay.com.au/itm/Aluminiu...5-5eec3be7154d
There's cheaper stuff, but this one is the goods. I was not about to buy an untested product and cross my fingers that it would work the same way. I was after something that was proven & would do the job without me needing to reinvent the wheel.
Only for non-ferrous metals.
Different types of aluminium is not a problem either as often needs to be with Al, that is most Al welding has be be between same parent alloy & matching welding rod.
You MUST follow the instructions on how to use this stuff. Do not apply the heat source (blow torch) directly to the rod. You feed the rod to the heated metal - see the instruction videos.