The 
NUPROL RZR BIO Tracer Green 0.28g BBs come in a bottle of 2,200 rounds and are designed for use in airsoft guns with a tracer unit. They are a popular choice for outdoor skirmishes due to their weight and biodegradable properties. 
Key Features
Weight: 0.28g, suitable for outdoor use as they offer better wind resistance and stability than lighter BBs.
Quantity: 2,200 rounds in a resealable bottle.
Tracer: Infused with material that glows green when activated by an airsoft tracer unit, making the BB trajectory visible in low light conditions.
Biodegradable: Made from materials that break down naturally over time, meeting international standards (ISO 14855-1:2012) and making them acceptable for use at most airsoft sites.
Precision: Manufactured to tight tolerances of 5.95mm +/- 0.01mm and triple polished for enhanced flight performance and reliable feeding in tightbore barrels.
Recommended Use: Best for replicas with upgraded hop-up units, performing well in guns shooting between 300fps - 400fps.