A bullet (blt) is a Vanilla option on an underlying contract that is generally composed of more than one monthly future, e.g., it is based on Summer 09 or Quarter 2. That is, it is an option based on a strip of futures. The underlying is an average of the underlying futures, and when the option expires you get a strip of the underlying futures.
This is different from a vanilla option whose underlying contract is based on a single future, and is also different from a vanilla strip which is simply a strip of vanilla options, each of which is based on a single future.
The underlying contracts supported for bullet instruments are as follows:
Monthly contract
Seasonal contract (the underlying is an average of the six underlying futures; when the option expires you get a strip of six futures)
Quarterly contract (the underlying is an average of the four underlying futures; when the option expires you get a strip of four futures)
Yearly contract (the underlying is an average of the 12 underlying futures; when the option expires you get a strip of 12 futures)
Pricing a bullet in SDX Commodities & Energy
When pricing a bullet (blt), note that it is only supported for commodities that support a bullet instrument, as follows:
European Electricity assets
NBP UK Natural Gas