As with air ranger , Stock is very similar, I bought a replacement tactical stock only as I didn't want to drill the walnut one, But basically where the shoulder of the bottle fits in the stock there is a piece carved out, There was enough depth for me then to drill the other side which is the underneath of the stock, First I used used a 2mm drill then behind with a 4mm Well actually it measured 3.98mm, Think the threads of the stud was 5.5mm , I did have to clear the hole drilled a little by gently drilling in and out a little, Measure the threads first on the stud as I've seen some different sizes, Daystate was selling some cheap stocks , walnut and tactical but I think they were for the wolf and rangers, Before fitting stud I put a couple of drops of oil in each hole, Now I have a sling fitted and it's made my life a lit easier with it, Taken me 8 years mind,