Vector files are the sharpest option as they never get "fuzzy" when enlarged.
Good vector files are .ai or .eps files where text has been converted to lines.
And pdf files can be suitable when they were generated from an eps file.

Please email the artwork you have available. When the correct format is not available we have software which will convert the picture to a eps file. When the conversion is not possible we can have the logo redrawn in the correct format for a very small fee.

Vector files do make a difference - see how from the two pictures below.
The first picture shows a bitmap file which when enlarged will get "fuzzy edges". Below that you will see the vector file which always stays sharp when enlarged. Remember the branding is your advertisment and the promotional product is the carier. Your brand MUST be properly reproduced.

Watch the word PLUMBING and see it in the pictures below when enlarged.