Here are 10 common types/sizes of laptop adapter pins/connectors

 

1. Dell 4.5mm Barrel (Yellow-tipped): Slimmer barrel with a center pin, common on newer Dell laptops (e.g., Latitude, XPS).
2. HP 4.5mm Barrel (Blue/Black): Similar to Dell's but often with a blue center, for mainstream HP laptops.
3. HP 7.4mm Barrel (Large Barrel): Thicker barrel with a center pin, used on older, higher-wattage HP business/workstation models.
4. Dell 7.4mm Barrel (Large Barrel): Older, larger barrel connector for powerful Dell machines.
5. Lenovo Slim Tip (Yellow/Black): A distinctive slim rectangular barrel, common on IdeaPads and Yoga.
6. USB-C (Power Delivery - PD): Reversible, oval connector supporting high power for modern ultrabooks (MacBooks, Dell XPS, HP Spectre).
7. Asus Barrel Connector (Various Sizes): Asus uses multiple, often specific, barrel sizes (e.g., 5.5x2.5mm).
8. Acer Barrel Connector (Various Sizes): Acer also uses standard barrel sizes, sometimes with unique center pin designs.
9. Toshiba Barrel Connector: Older Toshiba models often had their own proprietary barrel shapes.
10. Universal Adapter Tips: These aren't single types but collections (e.g., 10-piece kits) featuring various small, medium, and large barrel connectors, plus sometimes USB-C, for broad compatibility across brands. 

Key Identifiers: When buying, look for the Outer Diameter (OD) and Inner Diameter (ID) (e.g., 4.5x3.0mm) and the correct Voltage (V)/Amperage (A) for your laptop.