Monster

Works great!

Seal is a great solution for your subscriptions at a great price. I don't think Shopify's native sub app is working very well yet, so for third party solutions, check this one out. I had some initial kinks to work out with it, but their customer support has been very helpful and handled those issues. I'm always down with apps that have decent support teams - it's becoming such a rarity these days to get good support for anything! Definitely check this out.