These Debra's Garden needle sizers are accurate and beautiful. I've stocked them for a long time at p2tog.com but have recently had low stock. Today a delivery arrived, so I have many of the colours in stock.
metric (2mm - 10mm with some quarter sizes) and sock/lace (0.75mm - 4mm with many quarter sizes).
Debra also makes these row counters / yarn cutters. The inner dial counts 1-10 while the outer dial counts 10's. in th 50 position, a blade is exposed which is a handy yarn cutter.
All of these items are fitted with a split ring and can be worn as jewellery, used as a keyring or zip-pull.