These are cooling beverage cubes from the City collection by Orrefors (designed by Martti Rytkönen), whose main advantage is their reusability. What's interesting:

• The set includes 4 cubes made of stainless steel.
• They contain no toxic substances and do not absorb beverage aromas.
• They should be placed in the freezer for at least 2 hours before planned use.
• The cubes hermetically seal over 99% water and less than 1% ethanol.