This clock uses two separate bulbs with a granular material inside and an opening connecting the two bulbs. This means that the granular material/ sand would fall down on the bulb down below due to the mere effect of gravity. However, there have been variations in hourglasses too that were made over time. For instance, though hourglass clocks have always been in ampoule shape, their bulbs were not always connected. http://www.skyringecraft.com/sand-timer-hourglass/acrylic-sand-timer/

Portability refers to an object's ability to be moved, operated, stored, and/or carried. Portable shopping carts, then, are designed to be easily transported and take up as little space as possible. Striking the balance between functionality and portability can be challenging, though, especially if your store sells a number of large, heavy items. Still, certain features can enhance shopping cart portability without sacrificing their main function - to carry a certain capacity of products. http://www.tengtrolley.com/shopping-cart/

Most of the surgical hats are made up of fabric, and hence can be washed and reused. However, there are some disposable surgical hats available in the market for those functioning in extremely contagious or hazardous areas where it might not be ideal (or desirable) to reuse a surgical hat. Disposable surgical caps are an ideal fit if you work in highly infectious environments. http://www.zojemedicalproduct.com/disposable-surgical-clothing-for-medical-use/