Billabong Women's Sunny Rib Tropic Bikini Bottoms. Cross the line between swim and loungewear with the Sunny Rib Tropic. Adding substance to your staple bikini bottom, the solid is made from a rib knit swim fabric. The Tropic cut offers medium seat coverage and a low rise cut at the front and back. Features: Rib knit bikini bottom. Textured fabric. Tropic cut. Mid bum coverage. 1 inch less bum coverage than Lowrider bottom. Material: 94% Polyamide, 6% Elastane