H27W sits in Group 1 of the UN classification. As you likely already know, bulbs that belong to this class are always road legal. This obviously means you can use H27W lamps in projector and reflector headlights and many other locations.
However, for the best results, you may apply them as the parking, indicator, fog, reverse, number plate, and side position lights, as most informed drivers currently do.
The halogen bulbs are also dual beam. Do you know what that means? An H27W bulb has a single filament that serves the role of both low and high beams. They have a life span of about 1,000 hours. Furthermore, the H27W have PG13 base and are available in red, clear, amber, blue, and yellow colors, giving you plenty of options. Moreover, they produce 60 watts at 12 volts for your convenience.
The H27W comes in two versions. But they are the same in almost all aspects so there is no much worry about that. Given that the lamps use halogen, a few limitations may persist. For that matter, if you want the exceptional quality of light and a higher lifespan than ever, you need to upgrade your lamps to LED or Xenon HID.