I do not know since when they sell 3/16 inch headliner. Before I read about 1/4 inch they are/were selling:

You MUST use 1/8 inch headliner material and NOT 1/4 inch. WLS sells 1/4 inch for E32. 1/4 inch material will not fit contours of roof grab handles, and other recessed areas of Headliner, and the sunroof panel will bind and stick with 1/4 inch material because there is not enough clearance. Most European cars use 1/8 inch.
1/4 inch = 6.35 mm
1/8 inch = 3.1750 mm
3/16 inch = 4.762499999999999 mm

3/16 should/might be o.k., I assume.