About Setting blocks:
Setting Blocks are most commonly manufactured in EPDM. They are also manufactured in Silicone, Neoprene, and Santoprene.
A minimum of two setting blocks should be placed on each edge of the sash, serving to distribute weight evenly. The dimensions of the setting block are determined by the width and length of the IG unit ie. Larger panes require longer blocks. The gauge (thickness) of the setting blocks should be consistent on all four sides of the sash in order to promote even displacement.
Setting blocks are primarily used to stop glass from cracking, to maintain the integrity of the glazing bead and to protect the IG unit from sash impact. Silicone setting blocks are chemically compatible with all sealants tested to ASTM C1087.