DAC: Double-row angular contact ball bearing (steel balls); DU: Double-row tapered roller bearing (tapered rollers). Both appear cylindrical, but the internal rolling elements are completely different.

1. Visual Appearance (without disassembly)

DAC (ball type): Both ends have flat sealing covers, mostly black/red rubber seals, and a smooth cylindrical outer ring; for example, model name DAC39720037, size format DAC inner diameter × outer diameter × width. Commonly used in front/rear wheels of passenger cars, sedans, and small SUVs.

DU (roller type): Also cylindrical in shape, but with a stronger sealing structure (mostly ACM seals); model name DU25520037. Commonly used in vehicles with higher load capacities: SUVs, pickup trucks, and light trucks, bearing greater loads.

⚠️ It is difficult to distinguish them by appearance alone; you must check the engraved model number or disassemble to examine the rolling elements.

2. Internal Core Differences (Most Crucial)

① DAC: Rolling elements are steel balls, double-row steel balls, point contact; high speed, low noise; lower load capacity, cannot withstand excessive impact loads.

② DU: Rolling elements are tapered rollers, tapered rollers, line contact; large radial and axial loads, strong impact resistance; significantly higher load capacity than DAC for the same size; disadvantage: slightly higher noise at high speeds.

3. Concise Comparison Table