• Constructed From High-Density EPS (Expanded Polystyrene) Foam • Includes 4 PROVA LINEAR PAN® And 2 Side Supports Which Can Build Up To A 48 x 48" Linear Shower Base • Can Be Used With PROVA LINEAR PAN EXTENSION® (Sold Separately) To Extend Base To Any Desired Size Beyond 48 x 48" • Premium Polymer-Modified Thinset Mortar Required For Installation (Premixed Mortar Or Mastic Are Not To Be Used) • Mfg #TT8903CTR04