Suitable gels include those comprising silicone, e.g. a polyorganosiloxane system, polyurethane, polyurea, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-(ethylene/propylene)-styrene (SEPS) block copolymers (available under the tradename Septon??? by Kuraray), styrene-(ethylene-propylene/ethylene-butylene)-styrene block copolymers (available under the tradename Septon??? by Kur