Rechargeable lithium battery type 21700, 3.7V 4000mAh
Ultra Thin 3.7v 4000mah Li Polymer Battery For Laptop 3560105 In Stock - Rechargeable Batteries - AliExpress
Accessoires Energie - Batterie 21700 Li-ion 3.7v 4000mah
High Discharge Rate Battery 105565 Lipo Cell Voltage 3.7V 4000mAh Li Polymer Batterie - China Lipo Cell Voltage, Li Polymer Batterie | Made-in-China.com