The fire extinguisher neck ring proves the disassembly of the extinguisher during maintenance.
It must be stiff, unbroken, and have a snug fit on the fire extinguisher neck, so that it is impossible to place in position without removing the valve.
The rings have a different colour every year, depending on the last digit of the year as follows:

• Year ending in 0: WHITE
• Year ending in 1: YELLOW
• Year ending in 2: ORANGE
• Year ending in 3: BROWN
• Year ending in 4: GREEN
• Year ending in 5: BLUE
• Year ending in 6: PURPLE
• Year ending in 7: GREY
• Year ending in 8: CRIMSON
• Year ending in 9: BLACK