Difference between Off-the-shelf and Off-the-rack

What is the difference between Off-the-shelf and Off-the-rack?

Off-the-shelf as an adjective is as purchased or as commonly available, without modification or customization. while Off-the-rack as an adjective is ready-made in a range of standard sizes

We hope you now know whether to use Off-the-shelf or Off-the-rack in your sentence.