A burner body includes a wall that defines a combustible-gas chamber. The burner body further includes gas-flow inlet communicating with the combustible-gas chamber and a plurality of burner ports that permit combustible gas to flow from the chamber to an exterior of the burner body. The burner body further includes one or more flow restrictions configured to restrict flow through a proportion of the burner ports. When combustible gas is supplied at a first flow rate, each flow restriction is configured to restrict flow through an associated burner port at a first restriction ratio. When combustible gas is supplied at a second flow rate that is smaller than the first flow rate, each flow restriction is configured to restrict flow through its associated burner port at a second restriction ratio that is less than the first restriction ratio.