For owners S&T M249 Sportline, Laylax got available the Prometheus S&T M249 Sportline Selector Plate that can add a semi-auto function to it... "It is a selector plate for M249 sports line series made by S&T. By combining with the hard cut-off lever NEO Ver.2 (sold separately) , you can add a semi-auto function to the M249, which is only full auto. There is absolutely no troublesome wiring required for installation like an electronic trigger!
Not awesome looking upgrade parts but they'll do the job of staying longer and protecting your gearbox. These are reinforced anti-heat and anti-wear plastics and can fit existing G3 and MP5 AEG gearboxes up to 8mm in specifications. Both cost the same at Get Reload, where you can get them for US$8.50 which is a price worth putting up for if you want improved selector plates.
