Genuine Mastic. First in beautiful exteriors. Only the best. Mastic Home Exteriors by Ply Gem is your solution for the finest- quality vinyl siding products and our exclusive Designer Accents™ collection of finishing accessories. Shutters. Decorative door and window mantels. Corner posts. Blocks and vents. Columns and gutters. All designed to perform - and coordinate - perfectly with your Mastic siding. For uncompromising beauty and performance, insist on a complete exterior by Mastic Home Exteriors.