Alumi-Span offers a large variety of dock post, crossarms, platform trusses, and adjustable legs. Alumi-Span's standard size is 2 inch OD.  We suggest using 2 inch OD for all new applications.  All of our tubing related products are available in this size.  

It is very common for older dock systems to have 1.9 inch OD dock post and crossarms. Standard poles and crossarms are available in both sizes.  Please measure carefully if you are trying to retrofit an existing dock.  If in doubt please contact us.