An important class of random glass mat reinforced thermoplastics (GMTs), also called random continuous glass fiber thermoplastic composites, comes in the form of thermoplastic sheets containing nonwoven, random continuous glass fibers. Since the randomly laid glass fibers can uncoil with increasing deformation, heated sheets of this material can undergo large stretches without glass breakage. Blanks of this material can therefore be thermostamped (compression molded or flow formed in dies), at relatively low pressures, to form complex parts with deep-drawn regions, bosses, and ribs. These advantages make this class of materials – typified by Azdel^® P100 (Azdel PM 10400-101) composite sheet of 40 wt% random glass mat in a polypropylene matrix – ideally suited for large, stiff, low-cost parts that have high impact strength.