Is it possible to add just 1 variant to a product collection?

[BossBee]

Can I add 1 variant from product to a collection? Example I make whipped shea butter I have different size jars. I want only 4oz jars in a collection so I can add to my points program where people can get a 4oz butter free for their bday. 

if not is there a work around so my customers won’t   Be able to add the coupon to a product that’s not a 4oz jar 

[Liquid_xPert_SJ]

@BossBee 

The first option is only the way possible you need to create a single 4oz jar product and assign to that collection instead of the product that have variants, In other hands you can make coupon settings to only add for the product have 4oz jar.