比利时采购需求：双层玻璃咖啡杯、玻璃茶杯、玻璃酒杯、玻璃杯、玻璃壶、风暴玻璃瓶

We are in the process of developing a premium hourglass designed to accurately measure 60 seconds, with an allowable variation of ±5%. We're looking for a manufacturer that can expertly control sand flow and adjust the dimensions to approximately 110 mm in height and 60 mm in diameter. It's crucial that the glass used is high-quality and provides stable flow, and we're also interested in starting with a small initial order of around 100 pieces. Could you please clarify a few points? First, are you the direct manufacturer? Additionally, can you accommodate custom specifications for timing and design? Lastly, what is your minimum order quantity for custom products? Your prompt response would be appreciated.