Generally speaking, if you can add an item to cart: it is In Stock and ready to ship. Otherwise, you can sign up for In Stock Alerts on each product and you'll be emailed automatically when that stock is updated.
Some exceptions to what's In Stock include items marked as [Pre-Order] or print-to-order posters and most apparel.
The last and only other exception is an inventory error. We will contact you by phone and follow up with an email if we cannot fulfill your order for any reason.