Piezo discs are great for constructing pickups for acoustic instruments. Many users love them as the pickup in box guitars, and they are a favorite amongst people experimenting with electric drum triggers.This item is well made of for and practical use. Feature - - Material: Copper. - Size: Approx. 2.7 x 2.7 cm / 1.1 x 1.1 inch ( W). - Frequency: 4.0±0.5 Khz. - Impedance: 200Ω - Static : 25.0nFC30%at 100Khz. - Input Voltage: 30Vp-p - Operating Temperature Range: -20-70 degree centigrade. - Storage Temperature: -30-80 degree centigrade. - Plate Diameter: D=27.0±0.1mm. - Ceramic Disc Diameter: d=20.0±0.3mm. - Metal Plate Thickness: t=0.20±0.03mm. - Total Thickness: T=0.45±0.05mm. - Lead Wire Specification: UL1571 AWG 28# 2.54mm Terminal. - Features voice legible, contactless, thin and light. - 27mm brass outer diameter plate. - Low voltage and low power consumption. - Great for acoustic instrument pickups, boxes, mics, etc. - Suitable for clocks, toys, cameras, telephones and so on. Package list: 10 x 27mm Piezo Disc Diaphragm Elements Thicken Copper Sheet Piezoelectric Ceramic Chip with Leadwire