We tried a lot of different SMA-Male to N-Female adapters before deciding that none of them were good enough and started making our own instead. These adapters use high-quality RG142 cable that is durable and strong, and unlike most other adapters won't fall apart during installation.
This is a 50 Ohm impedance adapter (both N-type and SMA connectors are 50-ohm connectors).
The RG142 cable we use is double-shielded with silver-plated copper braid for maximum protection and performance. The 0.037 inch inner conductor is made of copper-clad steel with silver plating, and the inner dielectric is made from PTFE, while the jacket is a tan-colored fluorinated ethylene propylene (FEP).
The high quality materials allow for greater than 88dB shielding, and this high quality adapter is rated for use at frequencies of up to 6GHz.