It's about half as heavy as a Basketball
In other words, 0.310 kilograms is 0.497042191110 times the weight of a Basketball, and the weight of a Basketball is 2.0119016411 times that amount.(NBA official ball standards, Size 7)
A regulation NBA basketball, manufactured by Spalding, is known as a Size 7 ball and weighs 0.623689508750 kilograms. These balls have 4,118 pebbles each with a diameter of 2.5 mm
It's about two times as heavy as a Baseball
In other words, 0.310 kilograms is 2.13364452768190 times the weight of a Baseball, and the weight of a Baseball is 0.468681632308480 times that amount.(MLB rules)
Per Major League Baseball rules, a baseball must weigh between 0.1417476156250 kilograms and 0.148834996406250 kilograms. A major league pitcher can throw a baseball at up to 150 kph (91 mph) (with a fastball pitch), with record-setting pitches as fast as 171 kph (106 mph).
It's about two-and-a-half times as heavy as a Battery (D)
In other words, the weight of a Battery (D) is 0.4350 times 0.310 kilograms.(Alkaline)
A "D" size battery weighs 0.1350 kilograms. The D size battery is the oldest of the modern battery sizes, first invented by the National Carbon Company in 1898.
It's about three-tenths as heavy as a liter of Water
In other words, 0.310 kilograms is 0.30999130 times the weight of a liter of Water, and the weight of a liter of Water is 3.2258970 times that amount.(fresh; 4° C / 39.2° F; maximum density)
Contrary to popular belief, 1 liter (0.0.264172052358148 gal) of water at 4° C / 39.2° F (its point of maximum density) weighs 1.000028 kg rather than 1 kg exactly. The total volume of water on the planet Earth is about 13,590,000,000,000,000,000 (13.59 quntillion) L (3,590,000,000,000,000,000 gallons).
It's about three-and-a-half times as heavy as a Deck of Cards
In other words, the weight of a Deck of Cards is 0.30 times 0.310 kilograms.(ISO 216 B8 size, a.k.a. "poker size" 63 x 88 mm, 52-card deck)
A deck of 52 ISO 216 B8-size playing cards weighs 0.094 kilograms. Utilizing nearly 3,700 decks, the record-holding largest card tower was built in early 2010, stood over 3.5 m (11 ft), and weighed over 272 kg.
It's about one-fourth as heavy as a Human Brain
In other words, 0.310 kilograms is 0.230 times the weight of a Human Brain, and the weight of a Human Brain is 4.350 times that amount.(adult)
The average weight of an adult human brain is between 1.350 kilograms. In humans and primates, sight and vision utilize about 30 different parts of the brain which together account for about half of the brain's size.
It's about five times as heavy as a Battery (C)
In other words, 0.310 kilograms is 4.80 times the weight of a Battery (C), and the weight of a Battery (C) is 0.210 times that amount.(Alkaline)
A "C" size battery weighs 0.065 kilograms. C batteries are typically used in medium-drain devices such as musical instruments.