Im not sure what the sd designation is but I have several summit stands I am planning to sell. They are all the aluminum models and are in great shape. I bought them all new have used them mostly as a hang on even though they are climbers. No stand is any more comfortable. I will send pics of what I intend to sell there are different models. I am in Nashville area and rather not go through the shipping process for cost and time so let me know if that is a problem