400mm THK Linear Bearing Guide Rail 20mm 2 Blocks SSR20/YP8C369-KB Rear Thread

THK Linear Rail with Two Bearing Blocks. 400mm length (~15.75"), 20mm width, 15.5mm height. Rail is threaded from below. Hardware looks to be M6. 

I see small spots of surface rust, please see photos. Action is very smooth. 

Item weight is 1.9 lb.