No powder is needed on the inside. It pulls easily and uniformly. It eliminates all of the difficulties and inconveniences you experience with other materials.
Orfitrans Extra Soft Silicone is available in thicknesses of 9 mm and 12 mm.
ORF-37SIL/4490 Orfit Trans Extra Soft Silicone, 400 x 400 x 9 mm
ORF-37SIL/44120 Orfit Trans Extra Soft Silicone, 400 x 400 x 12 mm