Blum Tandem Premium Undermount Slides With Integrated Soft Close Full Extension For 12" Drawers 100# Class Full extension for 1/2" & 5/8" drawer side. 12" Drawer requires 12-3/4" Minimum Interior Depth For inset applications increase Minimum Interior Depth by drawer front thickness Undermount to drawer - Side-mount to cabinet, Rear-mount with bracket, Search: Blum Rear Mount Locking devices are required, Search: Blum Locking Device For Tandem Drawer Slides Also helpful, Search: Blum Tandem Accessory Kit