off-the-shelf vs off-the-rack

off-the-shelf and off-the-rack both are adjectives.

Word	Noun	Adjective	Verb	Adverb
off-the-shelf	No	Yes	No	No
off-the-rack	No	Yes	No	No

As adjectives, off-the-shelf and off-the-rack are synonyms defined as:

off-the-shelf and off-the-rack: (especially of clothing) made in standard sizes and available from merchandise in stock

Other synonyms of off-the-shelf include off-the-peg, ready-to-wear.

off-the-shelf (adjective)	off-the-rack (adjective)
(especially of clothing) made in standard sizes and available from merchandise in stock	(especially of clothing) made in standard sizes and available from merchandise in stock