The edges of these silicon frames are specially truncated with two parallel flats, which act as an aid for specimen alignment in Correlative Light & Electron Microscopy (CLEM) experiments.
These CLEM grids without a silicon nitride membrane are available in a variety of different size apertures and patterns.

The CLEM grids are 200 m thick and 3 mm in diameter with two 1 mm-long parallel flat edges on both sides.
The grids have a 50 nm silicon nitride layer on the back side with bare silicon on the front side.

Use of the parallel flats on both sides of the CLEM grid allows the orientation and alignment of the sample to be maintained when using different imaging techniques.