Metric & Imperial Bearings - ABEC 5 NMB metric and imperial bearings manufactured to ABEC 5. The bearings are suitable for use with precision instruments, chart recorders, etc. Manufactured from corrosion-resistant steel, the bearings are available in two designs: plain and flanged. The metric and imperial bearings incorporate double metallic protection shields, and the metric plain bearings are also available in Chromium Steel.