Hourglass 1) Solid wood frame 2) Logo with laser printing 3) Size: 5"-15"H 4) Timing: 2-30 minutes Specification of hourglass1. It has two connected vertical glass bulbs allowing a regulated trickle of material from the top to the bottom. Once the top bulb is empty, it can be inverted to being timing again. 2. Factors affecting the time include the amount of sand, the bulb size, the neck width, ...
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