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.
So it needs to be tough. Low-cost bench vises often use steel, which is light and cheap. It's fine for light duties and for hobbyists, but it doesn't have the high resilience a professional would need. The best bench vises are made of cast iron, and two variants can be found: gray iron and ductile iron. Gray iron isn't about color, it's used to indicate the presence of graphite flakes. It's the most common form of cast iron, used in everything from vises to stove tops.