The 'WM' Design barrel is an effective tool for recovering cores from friable and caving strata. The construction of the barrel is similar to the swivel type - double tube core barrel, except the core lifter is contained in a lifter case attached to the inner barrel. This allows the skirt of the lifter case to extend to the bottom of the diamond bit and protects the core from water washing, except at the face of the bit. The "M" Barrel is very useful for extremely sensitive coring requirements and where other type of barrels are not effective.