Works perfectly. The white you see on the bag is baby powder.
Read about it here:
The Caldwell Rock BR Competition Rifle Front Shooting Rest offers all the features found on other, more expensive bench-rest quality rests including coarse and fine elevation adjustments and finger-tip windage adjustment. The cradle is supported on ball bearings, the base is made of cast iron, there are stainless steel leveling feet, an adjustable forend stop, and bag tensioning adjustment. The Caldwell Rock BR Competition Rifle Front Shooting Rest gives you the stability you need to shoot the tightest groups possible. Accepts all Caldwell Deluxe Front Rest Bags and includes a 3" Lobe Bag (unfilled) and a Medium Varmint Bag (filled).
Technical Information:Caldwell Rock BR Competition Rifle Front Shooting Rest
Weight: 13 lbs.
Elevation Adjustment Max: 6"
Elevation Adjustment Min: 10-1/4"
Shooting Bags Included: Yes
Number of Shooting Bags: 2
Front Bag Adjustable Width Max: 9"
Front Bag Adjustable Width Min: 6-1/2"
Cradle Post Thread: 7/8-6 ACME