When selecting bearing adapters (such as H, HE, HA, and HS series), you must prioritize dimensional accuracy and material grade. Ensure the adapter sleeves are made from high-grade carbon steel (e.g., Q235 or C45) to provide the necessary tensile strength. Key specs include the taper angle (typically 1:12 or 1:30), which must be precise to ensure a secure fit between the shaft and the bearing inner ring. Additionally, verify the surface roughness (Ra value); a smoother finish reduces friction and prevents premature wear.