Cabo is one TALL Spanish Mastiff! Published on October 29, 2016 by Hoof and Fang Spanish Mastiffs This fencing is 6’8″ tall. Cabo will be a year old on November 13th. He will grow in height for another year, at a much slower rate, and will fill out until he is about 3 years old. Share this:TwitterFacebookPinterestLike this:Like Loading...