High density urethane foam board also known as HDU board is used for hand-carved signs as well as CNC-machining. RAKU TOOL Styling Board (SB) has a fine surface structure and lends itself to both manual and mechanical processing. Precision Board Plus™ High Density Urethane (PBLT) is a “closed cell” rigid polyurethane product made specifically for applications of up to 200° F ntinuous exposure.