It’s 14” and it does requires to have a channel milled for it to set into. Then use some T-nuts and screws to clamp it together. I used the ingenuity proprietary Dove tail style rail but opted not to add this to my stock.
As for the A10 don’t they have some different angles on the bottom of the fore end? These are designed for flat bottom like the Manners T4a,T2 etc