Top and side compression plates are plastic. Hdpe maybe. Machined with threaded inserts.
Bottom is aluminum plate. In contact with aluminum separator plates. White paste stripes in picture.
Sonic welded buss bars.
The assembly is then potted.
10s 70ah lto pouches. 300a continuous in this application. 500a surge.
15 of these are mounted in an 8' high enclosed "mini-grid" system.