TechPowerUp checked out the Noctua NH-D12L
A quote from the article:
Noctua looks to conquer the small form factor cooling market with the NH-D12L. With its maximum height of 145 mm, it fits standard 4U rackmount chassis and a wider range of Mini-ITX cases than traditional tower coolers. Add exceptional long-term support, good performance for its targeted market, and low noise levels and you have a solid offering for those limited by height.Noctua NH-D12L Review