Here are the common capacities of USB flash drives:

128MB: 128MB USB flash drives are becoming outdated and are rarely seen in the market.

256MB: 256MB USB flash drives are also becoming less common and may not meet the needs of most users.

512MB: 512MB USB flash drives have mostly phased out of the market.

1GB: 1GB USB flash drives may not meet the needs of most users.

2GB: 2GB USB flash drives are currently one of the most common capacities in the market and are also affordable.

4GB: 4GB USB flash drives are also common and come at reasonable prices.

8GB: 8GB USB flash drives can meet the needs of most users and are also reasonably priced.

16GB: 16GB USB flash drives can meet the needs of a majority of users and are also priced reasonably.

32GB: 32GB USB flash drives have a large capacity and can store larger files, and are also priced affordably.

64GB and above: USB flash drives with capacities of 64GB or more have a very large storage capacity, but also come with a higher price tag.