These adapters use high-quality RG178 semi-flexible 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 U.FL connectors are 50-ohm connectors).
The RG178 cable has a gold/nickel-plated solid brass center conductor. The adapter is VSWR test at < 1.15 for use at frequencies of up to 6 GHz.
U.FL is also referred to as IPEX/IPX/MHF/UMCC.