A shield consists of a conductor wrapped completely around the wire that requires shielding. Foil shields are inexpensive, and work fairly well, but require a drain wire to be grounded well, and it can tear when subjected to repeated flexing. Braid shields typically perform better than foil shields, but small gaps in the braid can allow higher frequencies through. The combination of foil and braid can provide excellent protection against EMI, but will cost more. Spiral shields can be used as an alternative to braided shields when high flexibility and flex life are very important. However, spiral shields can suffer from inductance at higher frequencies due to the spiral layout of the wires.