... 1.airtight waterproof rubber cushion 2.compression gas spring designing 3.saddle-backed shape 4.304 stainless ... ,One is not bottom ,it is install on rear seat of Honda 3 wheels scooter,The other one ... it also have two choose,include gas spring and not include gas spring.It is made of FRP(Fiberglass-Reinforced ... resistance, good tenacity. fibergalss super large volume scooter rear box with gas spring