They are compatible with the following models.
Diamond Clean, FlexCare, FlexCare+, Healthy White, and Easy Clean models
If you change your toothebrush head every 3 months this would give you a two year supply.
The fine print – Limit 3 per person, +$2.99 shipping rate
You can grab the deal here – Philips Sonicare Toothbrush Replacement Heads
This is better than any coupon deal I have stumbled upon!