You're most likely on this page because the item you're looking to purchase is currently out of stock! No one likes to wait, so our goal is to deliver your mods as quickly as possible. One way this is done is through pre-orders.
Let's set the stage. The modification you're wanting to purchase is out of stock and you're looking to have it shipped out as soon as they're back in stock. By purchasing now and placing a pre-order, we are securing that item for you ensuring whenever our next shipment arrives, you're first in line to receive the product. This is especially important because some of our most popular items are on a revolving backorder which means they're being sold quicker than they can be kept in stock.
It is better to order now and have the item security, than wait for an impending restock that may not have enough items to fulfill all pre-orders!