- Belt
- Read the width across the top (3/8", 1/2", 5/8") and measure the outside all the way around — a string around the belt, then the string against a tape. A worn belt stretches, so the number printed on it is better than the tape. Type it as 1/2 x 38.
- Tire
- The size is on the sidewall: 20x10.00-8 is 20" tall, 10" wide, on an 8" rim. The rim is the last number. A tube is bought by the same size.
- Saw chain
- Three numbers: pitch (3/8", .325", 3/8" low profile) and gauge (.050", .058", .063") are stamped on the bar near the saw; count the drive links — the teeth that ride in the bar groove — all the way around.
- Trimmer line
- The diameter: .065", .080", .095", .105", .130". Thicker is for heavier brush; the head's manual says the largest it takes.
- Blade
- Length tip to tip, the center hole (round, star, or 5-point) and its size, and the distance between any outer holes. Bring the old blade if you can — two blades an inch apart in length do not fit the same deck.
- Spark plug & filters
- The number is on the part: along the plug's ceramic, printed on the filter. Type it in; a cross-reference finds the same plug under another brand.