buy, get, etc. something off the shelf
buy (something) off the shelf
To buy something that is ready made for purchase from available stock; to buy something that is not custom built or crafted. We use our own custom software, so we can offer much more precision than what you can buy off the shelf. Yeah, if you buy a hearing aid off the shelf, it'll be less expensive, but they are much more prone to failure than those prescribed by a doctor.