This is a simple cheap DIY instead of speanding $40 for ContourHD Pictanny mount.
This was also on
http://www.dnkholdings.net but my version is for Canadian that have access to Home Depot and giving out the codes.
This was literally a $1.04. But you need to get a $10 Winglock mount.
Go to Home Depot.
Go to the Screw/Washer/Nut bins and search for these.
Excuse me but I forgot the size.
BIN# 4108 (NYLON SCREW) x2
BIN# 3977 (NYLON NO.6 WASHER) x2 (EDIT: YOU DON'T NEED THESE!)
BIN# 4076 (NYLON NUTS) x2
Take your Winglock Mount and break one arm.
Then you take your 2 screws, cut the top. 2 sides to make it fit into the ContourHD slot. Should be stiff, if it's really loose, you cut too much and go buy another $0.32 of screws.
(EDIT: YOU DON'T NEED TO PUT ON THE WASHERS!)
Here is washers on. Make sure you leave the screws into the bottom slot and make sure the wing is on the bottom side.
Then nuts. Make sure you also shave the end of the screw because it sticks out.
There you have it. A cheap mount that saved you $40.
Don't have my ARC rail in yet, but will update when I get pictures.