The dual-layer system on the Zettyo Syngergy is called "Bipolar System", which uses two different material to produce an unique feeling. The outer material of Zettyo Synergy is firm but not hard providing a tight feeling during use. The inside wall are lined with small nubs and large ribs made with another material to provide a stronger/softer stimulation depending on the model you choose. The large inner chamber along with the small entrance allows for great vacuum feeling simply by squeezing air out when inserting.
Zettyo Synergy Arisu has a two stage system of internal structure. The beginning is made up of a series of tight ribs leading into a large air chamber covered with long nubs. Arisu's "Bipolar System" has a softer inner layer compared to Mami and Yuuna.
*Use only water-based lotion or lube with this product.