alright guys this is my stupid question for this week but iv seen a lot of pictures of scopes with really long tubes (example: http://www.tactical-life.com/online/wp-content/uploads/2009/02/accupoint_5_20x50_hr.gif) and iv looked around at some leupold scopes and around at some other brands and i cant really find them. What are they exactly and what brands have them.