In plastic with an address (both to and return addresses) inside. I used to send UPS but found that the cost is higher and I don't like that they drop things on the front porch so often--even when I'm home. USPS--my postal clerks always weight and factor the destination and then advise whether the flat rate or first class priority is best--I always ask that it not be left on a front porch--if sending to some place like an apt I'll usually spring for a signed return receipt--it's only about 2-3bucks extra. That way it doesn't get left on the porch.