It's Structure Is That The Outer Ring And Inner Ring Are Integral, Which Is Suitable For Parts Requiring High Rotational Accuracy In Both Inner And Outer Rings. The Design Of This Series Is Integral Structure With Filling Holes , Which Avoids Adverse Effects On Bearings During Installation. Because The Inner And Outer Rings Have Machined Installation Holes, There Is No Need For Fixed Flange And Support, Which Is More Conducive To Installation And Is Mainly Used In SHF/SHG Series Harmonic Reducer For Robot . http://www.hnzkmachinery.com