Grabits are microwave-safe cookware easily identifiable by their tab handle. They were introduced by Corning Glass in the early 1970s, and are now sold in a slightly different form by World Kitchen. Grabits are notable in that they were some of the first cookware specifically designed for microwave use - their design was recognized by the Smithsonian's Cooper-Hewitt, National Design Museum

Cooper-Hewitt, National Design Museum

Cooper–Hewitt, National Design Museum, a subsidiary of the Smithsonian Institution, is the United States' national museum of design history and contemporary design and the only museum in the U.S. whose collection is solely focused on contemporary and historic design...

.http://www.nationaldesignawards.org/2009/honoree/smart-design Grabits strongly resemble porringer

Porringer

A porringer is a small dish from which Europeans and colonial Americans ate their gruel or porridge, or other soft foods.Porringers were shallow bowls, between 4" to 6" in diameter, and 1½" to 3" deep; the form originates in the medieval period in Europe and they were made in wood, ceramic, pewter...

s. They can be covered with a plastic lid, P-150-C, or a Pyrex

Pyrex

Pyrex is a brand name for glassware, introduced by Corning Incorporated in 1915.Originally, Pyrex was made from borosilicate glass. In the 1940s the composition was changed for some products to tempered soda-lime glass, which is the most common form of glass used in glass bakeware in the US and has...

 clear glass lid, P-240-C.

History

Grabits were originally produced and sold by Corning Glassworks, and made from Corning's unique pyroceram material. When the Corning Visions line was introduced, Grabits made from Pyrex Visions glass were added to the product line. After World Kitchen bought Corning Glass in the early 1990s, Grabits began to be made of ceramic, and production was moved from the US to China.http://www.corningware.com/index.asp?pageId=99