圓角處理，厚度約0.8mm，符合NEMA標準。
      鋅板通常用于確定研磨砂條如S-42的磨耗速率。
      S-34鋅板每面研磨次數不得超過十次。
      S-34 Zinc Standardization Plates are used to evaluate the abrasion characteristics of S-42 and S-33 sandpaper strips. Each plate is 4” square, .032” zinc with ?” center hole. (5 pcs.)