After creating a product with product items you have the ability to remove a product item if you wish to no longer see it when members select the product on the registration form.
1. Go to REGISTRATIONS > PRODUCTS.
2. Click into the relevant product.
3. Go to the ITEMS tab.
4. Untick the ACTIVE checkbox against the relevant product item.
5. Click UPDATE.
The particular product item will now no longer be visible when a member selects this particular product within a registration form.