Broforce Airsoft has the best brands of bb's in it's assortment, including; Xtreme Precision, G&G, Nuprol, Madbull, Geoffs & Green Devil. We only sell biodegradable bb's, so you can play on all Dutch and Belgian pitches without any problems.
If you are going to play outside, it is important to shoot with future bb's. External influences (such as wind) can prevent light bb from flying nicely in a straight line. If you play with a DMR or Sniper Rifle, it is allowed in the Netherlands to use heavier bb's than .30g. Within this class the .32g - .40g bb's are allowed on the Dutch fields.