Calvin Klein Invisibles Triangle Convertible Strap Bralette (QF5753). The Calvin Klein Invisibles Triangle Convertible Strap Bralette QF5753 is the perfect wardrobe basic with a line-free construction and straps that can easily be converted to a crisscross. Calvin Klein's Invisibles Triangle Convertible Strap Bralette is made from polyamide and elastane.