I've seen a lot of cooktops, some rated to be used with LPG (liquid gas or propane) and others with natural gas. Some companies have 2 models of the same design (one for LPG and one for natural gas).
What is the difference between the two? is it just the connector type or is it a different design of the cooktop burner itself? Is it possible to 'convert' an LPG cooktop to natural gas (and vise versa) or is it a completely different design and there is no point in trying to convert?