Some ep's will come with a x2 barlow attached as standard, the TBM's are one such line. These barlows will unscrew, allowing you to use the one ep at two levels of magnification.
There is normally a fairly clear line at the base of those ep's that have a barlow attached. So a 9mm will give you a 18mm/9mm combo without and with the barlow etc.
Something to look for when reading reviews as you can get two for the price of one on some ep's though normally the whole line does not include them. Nor will they always be x2 barlows, they can be x1.5 etc.
