Boeing’s [BA] contract to build the tail kit that will guide the B61-12 nuclear gravity bomb during free fall is worth $215 million over four years, according to an Air Force procurement document released last week.

The Air Force Nuclear Weapons Center at Eglin Air Force Base in Florida released the initial funds for the sole-source tail kit assembly contract in May after announcing in December that Boeing’s design was ready for production. However, the service did not disclose the financial terms of the pact until Wednesday, when it released its Justification for Other Than Full and Open Competition.

The National Nuclear Security Administration (NNSA) is building the B61-12 gravity bomb itself. The weapon will homogenize four existing versions of the oldest active U.S. nuclear weapon, one of which is an earth-penetrator. On Thursday, NNSA Administrator Lisa Gordon-Hagerty disclosed that the semiautonomous Department of Energy agency will be late delivering the B61-12 to the Air Force because of problems with non-nuclear capacitors needed for the weapon.

The NNSA had planned to deliver the first B61-12 in the government’s 2020 fiscal year, which ends Sept. 30, 2020. The last B61-12 was slated to reach the Air Force by 2025. The agency has not yet quantified how long the capacitor issue will delay deliveries, or how much the problem will cost the civilian agency.

The Air Force is responsible for integrating the NNSA-made B61-12 with carrier aircraft including versions of the B-2 bomber, the planned B-21, the F-15, F-16, F-35, and the German-made PA-200, according to the Air Force Nuclear Weapons Center.

Including Air Force and NNSA work, the B61-12 will cost between roughly $11.5 billion and $13 billion over about 20 years, according to documents from the Energy and Defense departments. The NNSA’s share of the bomb’s cost is about $8 billion, the agency estimates.

The Washington-based nonprofit Federation of American Scientists estimates the NNSA will build 480 B61-12 bombs.