ECCO. 836734-02001. ST. 1 HYBRID CHUKKA BOOT. BLACK. The ECCO ST.1 Hybrid Chukka Boot lends a distinguished casual look. Featuring a PHORENE midsole with FLUIDFORM Injection technology this ankle boot offers unparalleled softness increased shock absorption cushioning and rebound while the SHOCKTHRU shock point and durable thermoplastic outsole provide excellent durability and support.