The Sachtler Accessory Adapter, article number 3985, is designed for fluid heads equipped with an adapter viewfinder extension and adapter block. It provides tapped holes for 1/4-inch, 3/8-inch and M8 accessory fasteners, allowing additional accessories to be mounted to the fluid head. The adapter measures 40 mm in length and 25 mm in height and has a specified weight of 0.1 kg. Material and width are not specified.