You can change the size of interdental brushes that are sent out in the refills; however, this needs to be done with a minimum of 24hrs notice before a subscription renewal is due. This can be done by heading to your online account and selecting “your Plan”.
This will show you your next renewal date, subscription frequency and your active subscriptions. From here you can pause the subscription or click on the subscription and expand the details to update brush sizes.
Once you click on your active subscription you will then see the above option with the refill you have selected from your account. once you have selected this refill by pressing the down arrow to expand the refill you will see the below page.
Here you can edit the refill by changing any additional options that the refill has such as the colour of the brush head and the sizes of interdental brushes you receive on the recommended refill.
Once you have made your changes to the refill click "CONFIRM" to save these settings to your account.