Also - just some advisory:
#1 Sign it with your name/watermark and
#2 give them a smidge, not the whole thing.
Don't give them your idea for free!
Degrade a portion some how, in some way.
I know you want to show it off, but don't let them pass on you but take your work.
I absolutely hate when artists inadvertently fork over exact specific concepts for free.
Give them work that has NOTHING to do with the product advertised.
ie - So, if it is a soap bottle they want, give them a soda bottle, to show your power, or a vase with water or something....
but do not give them a direct example soap bottle freebie. But do mention, specifically, that a soap bottle is very doable by you, and that you would love to work with them on a product.
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