What does the U of the badminton racket stand for?

Update:10-11-2018
Summary:

U stands for the weight of the badminton racket. The co […]

U stands for the weight of the badminton racket. The common standard for the weight of the badminton racket is U, 2U, 3U, 4U. The weight of the general all-carbon badminton racket is mostly 2U (90-94g) or 3U (85-89g), 4U (80-84g), while the weight of the aluminum frame badminton racket is generally above U (95-99g). .
Heavier racquets are for players with good strength and offensive, and lighter racquets are more suitable for defensive players.