Bollards are permanent or removable metal posts designed to block vehicles.  You see them mostly in parking lots in front of businesses, or at entry/ exit points on property to deter entry.  There is no standard size, but 4" and 6" round bollards are more common.  The can be installed with concrete as a permanent fixture, but there are also a variety of lockable and fold down options.  You can have the metal powder coated in a bright color for visability, or you can purchase a sleeve for them.  Colored sleeves are commonly yellow or red with reflective striping, but some are plain.  We can purchase standard items, or our manufacturing shop will make bollards to your specifications provided.  It's best to do your research and figure out what you want as we cannot tell you what's necessary for your property or a specific job.  We like to make things easy for all our customers.  Anything custom manufactured needs to be made to the specifications provided by the customer.  We can show you examples of bollards we have made in the past.  Please let us know if you have any questions about bollards and we look forward to working with you.