Let us have a look at RG316 thin coax used in baluns and chokes

RG316 is a small diameter coaxial cable with silver-covered copper-clad steel stranded inner conductor. That means the innermost layer is steel, providing strength, followed by copper clad next layer. Surface of the wires strands are covered with silver for better conductivity. Typically 7 strands of 0.0067 inch diameter wire forms the inner conductor. Dielectric layer is made of solid PTFE (Polytetrafluoroethylene), which provides good electrical insulation and has a wide operating temperature. Shield is made of silver-plated copper braid. The outermost protective sheath is made of fluorinated ethylene propylene (FEP). Nominal impedance is 50 ohms and the outer diameter is 0.1020 inch while inner conductor diameter is 0.0201 inch. It is quite tiny to deal with.