Pro Tip: Look at your Amazon orders and see if your add-on items are sent, here. Your order needs to be over $25 for your add-on items to get included.
Add-on items are cheap items that aren't cost effective to ship on their own. You're able to make an order of $25 made entirely of add-on items. Or, make an order of more than $25 and include your add-on items to that order.
Either way, your purchase needs to be $25+ in order for your add-ons to get included in the shipping. Only items that cost less than $25 are eligible to be add-ons. This Amazon feature allows you to save on your delivery fees for small items.
You get your smaller items sent in one-go with your larger items, or all together in one package. Get the best prices and deals on multiple add-on items on Amazon, here.
To get the best value for your money, check out Amazon prices, here. Save big and get the best prices, with a variety of items to choose from.