Hi, This is a type of 4 Layer PCB mixed 20mil (0.508m) RO4350B and 0.6mm FR-4 for the application of Low Noise Amplifier. It's multiblock construction, so there're few different boards inside. Keep out lines are outer contour of the milling cutter. When you have several different prototype PCB jobs for trial market, this is a good economical way to help you save the production cost that is merging these different PCBs together to be manufactured simultaneously on one panel. Finished PCB products can be formed in panel with breakouts and can be individual boards too. Basic specifications Base material: RO4350B 0.508 mm + FR4 0.6 mm + PP 0.306 mm Layer count: 4 layers Type: Mixed multiblock milled with bridges Format: 225mm x 182mm = 6 types = 12 pieces Surface finish: Immersion gold Copper weight: Outer layer 70 um/ Inner layer 35 um Solder mask / Legend: no / no Final PCB height: 1.6 mm Standard: IPC 6012 Class 2 Packing: 5 panels are packed for shipment. Lead time: 10 working days Shelf life: 6 months Application Mixer, Radar data acquisition converter, Spread spectrum, Duplexer Contact us today for more preferential price. Best regards Kevin Liao | Business development Bicheng PCB | www.bichengpcb.com| sales@bichengpcb.com |Material partners: Rogers, ITEQ, SHENGYI, TAIYO, KUANGSHUN If you do not want to receive emails from Bicheng about marketing communications and special offers, reply as “remove” in the subject line. Bicheng Serves Global Customers from Shenzhen, China 518103.