They are Imperial, - go for the 1 1/16" (26.9875mm) six-sided socket, which will do the least damage to the stainless steel covers.
If your nuts are in good nick... :wasntme: then invest in a top-quality socket, otherwise you may end up with a worn out or even re-badged 27mm. :twisted:
27mm should only be used if the covers are stuffed...and you don't have anything else...and you MUST get them off, right NOW.
Here's an online Conversion site, anything to anything. You may find it useful for metric/Imperial comparisons.
Online Conversion - Convert just about anything to anything else
James in Gosnells,
'95 Classic with working EAS...and wheels/nuts the same as you vehicle...

