This is a Silicon Flat Window, model SI-W-50.8-1, offered by Alkor Technologies. The window has a base shape of a circle with a diameter of 50.8 mm and a thickness of 1 mm. The material of the window is silicon, specifically silicon sal vil 1957.
The window is designed for use with a wavelength of 633 nm and has a shape similar to a thin lens. It does not come with any coating, making it uncoated. According to the vendor's website, this item is currently in stock.
For more information about this product, you can visit the vendor's website using the provided weblink. The weblink status is valid, indicating that the link is working and leads to the correct product page.