E15 is the whitest of the 20mm x 20mm range of unglazed ceramic mosaic tiles however it is not a bright white, rather a slightly soft white so if you do need a bright white you should choose E201 in the 24mm x 24mm range.
SHEET SIZE - 196 tiles per full sheet, 98 tiles per half sheet & 49 per quarter sheet.
The individual tiles measure 20mm x 20mm x 4mm and the full sheet measures 305mm x 305mm.
.