Guides

Short, sourced answers to the questions behind the numbers.

Battery Codes: JIS, DIN and BCI Group SizesHow to turn a JIS code like 55D23L or a DIN/EN case like LN3 into a BCI group size, using BCI's own best-fit tables, with worked examples. Car Bulb Numbers ExplainedWhat H11, 9005, W5W and 7443 mean, how US trade numbers and ECE names relate, and which bulb numbers owner's manuals list most. Wiper Blade Sizes: Millimetres to InchesWhy a 600 mm wiper is sold as a 24-inch blade, a conversion table, and how to read the wiper size printed in your owner's manual.