Feedback Sports Scorpion Display Stand - 1-Bike 13-20mm Hollow Bottom Bracket Mount BLKFeedback Sports Scorpion Display Stand 1 Bike 13 20mm Hollow Bottom Bracket Mount Black. The Scorpion is compatible with 13 18 and 20mm hollow crank spindles on either side of the bike. The design elevates the rear wheel and lends itself to lite bike maintenance like chain lubrication and frame cleaning. Awesome bike storage for garages sheds apartments events or retail bike displays Versatile design allows for bike parking with 13 18 or 20mm open