It's simple, sign in to your mypura.com account and go to Account. Click on My Subscriptions and under Your Active Subscription you will see all the products you subscribe to. Select the subscription you want to change, click Manage, then click on the Swap Product option and you will see a list of all Pura products. Pick the product or size you want to switch to, and press Select. Check the quantity and the delivery frequency and amend if necessary and press Submit. The changes will then show in your active subscription summary!