4320 offers the best combination of fast strains and high-quality mushrooms. It is very successful as a fresh market mushroom because of its excellent keeping quality. It produces medium size mushrooms with very firm flesh. The colour is medium to dark brown depending on cultural techniques. The cap is well rounded when young and flattens as it reaches maturity. The first flush appears very strongly around 7 weeks after spawning. 4320 works well in growing systems using pasteurized substrates due to its aggressive growth in sawdust/ straw based substrates and its resistance to Trichoderma.