Anti-slip ratings are a European measurement for how slip resistant a tile is. The rating comes in the form of an 'R' (Ramp Test) value, which ranges from R9, which has a small degree of slip resistance, right up to R13, which is the highest slip resistance R9: Minor slip resistance, suitable for dry internal spaces such as a dining room or lounge. R10: Moderate slip resistance, suitable for bathroom floors. R11: Good slip resistance, can be used in all internal areas including wet rooms and can also be used outside.