Mitragyna speciosa is an evergreen tree that can grow to a height of 25 m (82 ft) tall and the trunk may grow to a 3 ft (0.91 m) diameter. The trunk is generally straight and the outer bark is smooth and grey.
Overall though, metal is a much better option than plastic. In most cases, it is much more effective and reliable, and the right choice of metal will avoid the pitfalls of rust or weakness. Aluminium, steel and stainless steel are the three metal gutter materials for guards that homeowners can choose from.
Both gold and cobalt-chromium have proven to be effective and biocompatible stent materials, though gold can be quite expensive. Tanatalum and nitinol are also promising, though the first can be somewhat brittle and the second difficult to manufacture. Ad. The other main type of stent material is polymers. Silicone is well-tolerated by the body, but it is not ideal when it comes to strength and durability. Polyethylene and polyurethane have the opposite problem.