Here is the professional, SEO-optimized English product description for your Infinix Hot 4 Pro replacement battery (Model: BL-39AX):

Infinix Hot 4 Pro Replacement Battery (BL-39AX) – 100% Premium Quality

Is your Infinix Hot 4 Pro losing power rapidly, getting stuck at low percentages, or shutting down unexpectedly mid-call? Bring back its factory-fresh stamina and long-lasting backup with our premium-grade BL-39AX replacement battery. Specifically engineered to meet strict performance benchmarks, this high-quality battery provides the steady, stable energy supply your smartphone needs for uninterrupted daily performance.

Key Features:

• Flawless Physical Fit: Tailored precisely for the Infinix Hot 4 Pro (Battery Model: BL-39AX / Model: X556), ensuring an exact structural match and secure connector alignment with your phone's internal logic board.

• True 4000mAh Power Capacity: Packs a full standard 4000mAh capacity to completely restore your device's multi-day standby performance and extended screen-on hours.

• Advanced Smart IC Protection: Equipped with an integrated intelligent safety microchip that actively shields your smartphone from over-charging, over-discharging, unexpected overheating, and sudden short-circuits.

• High-Density Lithium Polymer Cells: Built using advanced cell technology for ultra-stable voltage output, entirely eliminating erratic percentage jumps or unexpected power drops.