I use this ZOKU Glass Core Bottle & Tea Infuser daily for loose leaf tea. The stainless steel infuser is easy to fill and rinse, and the borosilicate glass core really does keep the flavor clean without any metallic aftertaste. The leak-proof cap and glass mouthpiece make sipping mess-free, even in my bag. It handles both hot and cold drinks fine. Only small note: loose leaves need a slightly coarser grind so they don't slip through. Solid for commutes and desk use.