Coarse Drywall Screws, Black Drywall Screws, Bugle Head Drywall Screws Ningbo Brightfast Machinery Industry Trade Co.,Ltd , https://www.brightfastener.comSerial number test project technical standard Class A (national standard) B level (national standard) Super B level (enterprise standard) 1 anti-theft door resistance abnormal opening time 15min 30min 30min 2 anti-drilling damage time 15min 30min 30min 3 anti-saw damage time 5min 10min 10min 4 Flood prevention time 15min 30min 30min 5 tensile damage time 15min 30min 30min 6 Anti-shock damage time 15min 30min 30min 7 anti-technical opening time 1min 5min 260min 8 Inter-opening rate ≤0.03% ≤0.01% ≤0.0003%