I've bought these to replace mine on my Coyote mountain bike with V-brakes.
They appear to be great quality and feel well made. The brake block itself is 68mm long with a slight curve to it's shape. It is easily attached with the use of a simple allen key. The washers are supplied so you can put them on straight out of the packet.
I've used'em cycling to work on the road with wagons and lunatic van drivers whizzing by and felt confident when braking. So it's all good! :)
Great value for money as you can easily pay double for these elsewhere!