The Shapers Blocks are widely considered as the Industry Standard

interchangeable hook&loop compatible Sanding Sheets .

Soft Block: Ideal for rolling off decks, shaping rails and finer finishing. Recommended for use with The Shapers Block Sanding Sheets or Gauzes in 150#, 180# and 240#
Medium Block: Excellent all-round Shaping Block. Whilst suitable with all grades, most commonly used with 80# and 120#. 
Hard Block : Ideal for the fast and effective removal of foam and therefore recommended for use with 60#.

Sanding sheets sold separately