Form 4 Filing for Eos Energy Enterprises, Inc.

Joe Mastrangelo, Chief Executive Officer and Director of Eos Energy Enterprises, Inc. (EOSE), reported transactions on September 14 and 16, 2026. On September 14, 500,000 performance-based restricted stock units vested, which were granted on July 5, 2024, based on total shareholder return. These units were acquired at a price of $0.00. Subsequently, on September 16, 250,000 shares of Common Stock were sold at a weighted average price of $3.92 (ranging from $3.84 to $4.16) to cover tax withholdings related to the vesting of these units. This sale was executed under a Rule 10b5-1 trading plan. Following these transactions, Mastrangelo holds 2,308,704 shares of Common Stock.