If you haven't already done so, upgrade to the flatblade wipers, I first did it to the girlfriends Focus then my Laguna as soon as I bought it.
The drivers side blade is 24" and I'm pretty sure that the passenger one is 20"
, but don't get the cheapest ones, they don't last too long.
Bosch ones are the best, but expensive. Go for £8 - £12 and you'll be fine.
Also, they ask you to check with your reg and they got mine right.
Alternatively, you could just measure them