Quantifoil R2/4 Micromachined Holey Carbon Grids, Copper, Pk 100, SPI Slide-A-Grid box
Quantifoil holey films with 2 µm circular holes are used with magnifications in the range of 30,000X to 40,000X. Quantifoil R 2/4 is probably recommended over R 2/2 when an increased tolerance with respect to position of the beam, and a larger beam diameter is desired, such as in the case of automated image acquisition. Quantifoil R 2/1 has more open area than R 2/2. It is usually used when focussing is carried out on the edge of a hole burned into the ice in a neighboring hole instead of on the foil adjacent to the hole.
The Quantifoil holey films are available on "standard, stock" grid mesh, namely 200, 300, 400, and 100x400 mesh, in Cu, Ni, Au and Rh plated Cu. Other grid meshes and other grid constructions are possible, of course, but on special order and for a higher price.