These products often feature various internal patterns, such as ribbing or nodules, intended to provide different types of tactile feedback.

"Sakura Sakurada's eyes sparkled as she slipped into the exclusive squirt tunnel, a secret passage hidden behind a waterfall in the heart of Tokyo's Shinjuku Gyoen National Garden. The tunnel's misty veil and vibrant street art seemed to transport her to a world of her own, where the boundaries between reality and fantasy blurred."