Set limits on Add-Ons
There are many ways you can set limits for Add-Ons. The drop-downs below provide more details about the possible limits.
Limit Inventory for an Add-On
When you are setting up your Add-On, you can set a total inventory for that specific item.
Navigate to the event, collection, or class where you have the Add-Ons attached. Then, next to the title, click Pricing --> Add-Ons.
Either create a new Add-On by clicking +Add-On or edit an existing Add-On by clicking Edit.
Under the section titled Variants, you can set a total inventory for a specific item. If you have multiple variants, such as "Small Shirt" and "Medium Shirt", you can set different inventories for each.

Click Save Changes at the bottom of the page.
Limit how many Add-Ons a patron can purchase
If you have a limited amount of a specific item and want to make sure you spread the wealth, you can set a limit on the number of Add-Ons a patron can purchase.
Navigate to the event, collection, or class where you have the Add-Ons attached. Then, next to the title, click Pricing --> Add-Ons.
Either create a new Add-On by clicking +Add-On or edit an existing Add-On by clicking Edit.
Scroll down to the section titled Limit Per Patron. Check the box for Limit Per Patron and insert the cap you'd like to set.

Click Save Changes at the bottom of the page.
Limit who has access to buy an Add-On
There are two ways to limit who has access to purchase an Add-On.
Set Access Type: When setting up an Add-On, there is a section titled Access. From this setting, you can choose whether all patrons and admins have access, only admins have access, or only people who log in with a pass holder code (such as a membership or flex pass holder) can gain access.
Set Passcode to unlock an Add-On: When setting up an Add-On, click Advanced Options at the bottom of the page and locate Special Passcode. Check the box for Enable special passcode, and then type in the code you'd like patrons to use to unlock this Add-On.

Then, when they are making a purchase, they can type in that code to reveal the Add-On.

When using a Special Passcode, you will still want to ensure that the Access setting is set to Everyone. This will keep the item hidden but still accessible if patrons utilize the passcode.