Square hollow capillary tubes in Borosilicate glass can be drawn to various sizes. These precision square glass capillary tubes have flat, thin, parallel walls for viewing microscopic objects in two optical planes at right angles. Tolerances of inner and wall dimensions are listed in the table below, and custom sizes with required tolerances are also available. With 13 years experiences in glass fabrication, self-designed equipment and highly qualified staff of engineers and technicians, we are ready to meet your most demanding requirements or simply ship from our stock catalog items.