According to the Pentagon, the package includes:Additional munitions for NASMAS
150 heavy machine guns with thermal imagery sights to counter Unmanned Aerial Systems (UAS)
Additional ammunition for HIMARS
200 precision-guided 155mm artillery rounds
10,000 120mm mortar rounds
High-speed Anti-radiation missiles (HARMs)
150 High Mobility Multipurpose Wheeled Vehicles (HMMWVs)
Over 100 light tactical vehicles
Over 20,000,000 rounds of small arms ammunition
Over 200 generators
Spare parts for 105mm Howitzers and other equipment

The $400 million is being sent to Ukraine through the Presidential Drawdown Authority (PDA), which allows President Biden to send arms straight from US military stockpiles.

The Pentagon is clearly scraping the bottom of the barrel.

Additional munitions for NASMAS

NASMAS is an air defense systems that uses re-purposed air to air missiles (active radar homing AIM-120 AMRAAM) in a ground to air mode.