This is not a camera mounting plate so having a 'knob' screw down is a bit confusing - but - it works for me as an improvised ( and cheaper ) HDMI shield plate when installed on the side rail of A7 series cage. Dimensions are not given in the ad but for those who need them. it is 30 x 50 x 4mm or about 1 1/8 x 2 x 3/16 inch for the plate size. 2 stainless steel hex head screws and the tool are supplied with the plate and the hole center distance between the 2 rows of threaded holes is actually 18mm.