# When Housing Width Is Only 3.5 mm: Specifying SMR128ZZ

A 3.5 mm width leaves almost no room for a standard shield stack or a thicker snap ring. That is why SMR128ZZ exists as an 8×12×3.5 mm stainless deep groove rather than a cut-down 608 or 688.

If the housing is already machined, do not open the bore or the width to fit a more common size. Check shaft fit, housing fit, and whether you need shields (ZZ) or a different closure. Stainless rings are the usual choice when the mechanism sees moisture or light wash fluid.

The SMR128ZZ bearing listing keeps this size separate from SMR105ZZ and SMR106ZZ. TFL Bearing can confirm stock and packing for instrument or medical-adjacent assemblies when you send the bore and width.