First, we need to determine the size of the flags and flagpoles to ensure they can be properly displayed and used at the Strawberry Music Festival.

For the size of the flag, we can consider the following factors:

1. The length of the flag: According to the size of the Strawberry Music Festival and the size of the venue, we can choose different lengths. Generally speaking, the length of the flag should be between 1 meter and 5 meters.

2. Flag width: We can choose different widths according to the length and design requirements. Generally speaking, the width of the flag should be between 30 cm and 1 meter.

3. Flag colors and patterns: We can choose different colors and patterns according to the theme and design needs of the Strawberry Music Festival. Generally speaking, flags should have bright colors and simple and clear patterns.

For the size of the flagpole, we can consider the following factors:

1. The length of the flagpole: According to the height of the flag and design requirements, we can choose different lengths. Generally speaking, the length of the flagpole should be between 1 meter and 3 meters.

2. Diameter of the flagpole: Depending on the length and design requirements of the flagpole, we can choose different diameters. Generally speaking, the diameter of the flagpole should be between 1 cm and 5 cm.

3. Flagpole color: We can choose different colors according to the theme and design needs of the Strawberry Music Festival. Generally speaking, the color of the flagpole should match or be similar to the color of the flag.

To sum up, we can choose the appropriate flag and flagpole size based on the size of the Strawberry Music Festival, venue size, design needs and other factors. Generally speaking, the length of the flag can be between 1 meter and 5 meters, and the width can be between 30 cm and 1 meter; the length of the flagpole can be between 1 meter and 3 meters, and the diameter can be between 1 cm and 5 cm. between.