Stealth Rotary tattoo machine replacement bearing. Fits both Stealth 1 & Stealth 2 rotary machines. The Bearing is available in 4 strokes: 4.5mm, 4mm, 3mm, & 2mm. How do I pick the bearing Stroke Length? If it depends on your "Needle Swing" preference. Most people prefers the 3mm or 4mm longer stroke bearing.