EG" most likely refers to the brand 
Enola Gaye, which produces armbands in various colors, including blue, for use in combat scenarios like airsoft. 
Product Information & Reviews
The 
Enola Gaye Team Armband - Blue
 is a popular choice for team identification in airsoft and similar activities. 
Design & Features: It uses a wide strip of Velcro for a secure fit that is "one size fits most". A quick-pull tab allows for fast removal, but the strong fastening ensures it will not fall off during play. The material is often neoprene.
Durability: According to the manufacturer's description cited on Combat South, the product is very durable, described metaphorically as "bullet proof, bomb proof".
Color Availability: The armbands are available in a variety of colors besides blue, including red, yellow, orange, light blue, olive green, white, and woodland camo.