Your very first shipment is the Triple Bristle starter kit, which contains everything you need to try the dentist created Triple Bristle sonic toothbrush, including a "starter" brush head designed to last 30-45 days and a tongue cleaner. This 30 day trial period gives you the opportunity to try the Triple Bristle and decide if it's for you.
The 30 day followed by every 60 day replacement head shipments contain "premium" brush heads that have blue indicator bristles that fade over time and last anywhere from 60-90 days.