But it DOES say "for vehicles equipped with SRS airbags" 
 
Someone with better grammar analysis than me can probably decode the nouns, adjectives and verbs 
Parse a sentence
They likely suit Defender vs County via different mounting brackets and/or the way the mounts are installed.
The mounting brackets are separate to the bar. You bolt the brackets to the chassis, and the bar to the brackets.
Looks like you also need to drill additional holes in both the bracket (to match the existing chassis holes) and the chassis (to fit the mounting bracket holes) for full and final fitment.
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