The Architect Series is our most unique office furniture to date. This bookcase frame is hand made from massive 2" thick steel tube which gives the desk an elegant and sophisticated presence. We used 1½" steel for the distinctive Architect rectagle, and ½" steel for the side rails which gives the piece a sleek and open feel. The side rails are 7½" apart on center, except for the 1st and 2nd shelf which are 6½" apart on center. The bookcase comes with 4 pieces of glass that can be placed in any order on any of the side rails, which allows you to adjust them for a variety of needs. A perfect match for the Architect Desk, these pieces are the strongest, and in our opinion best looking, office furniture you can find anywhere. The bookcase is hand finished and the powder coat of your choice is applied. The 4 glass shelves are 15" x 36" and are ⅜" thick.