Illustration: the five trimmer head styles compared in this guide.
If you own a Stihl FS45, the head you want threads on at M8 x 1.25 left-hand and is built for 2.0 mm (.080") line. Below we compare the OEM STIHL head against the most popular aftermarket options on specs, fitment, and price — so you can pick the right one without guessing.
What to check before you buy
- Thread size. The FS45's shaft is M8 x 1.25 left-hand thread. Any head you buy must match this (directly, or via an included adapter). When in doubt, check your thread size before ordering.
Illustration: trimmer shaft thread detail — match your head to the M8 x 1.25 left-hand spec.
- Bump feed vs. auto feed. Bump-feed (tap) heads advance line when you tap them on the ground — simple and reliable. Auto-feed heads advance line automatically but can waste line. Most FS45 owners stick with bump feed.
Illustration: inside a bump-feed head — spool, spring, and line eyelets.
- Line diameter. The FS45 ships set up for 2.0 mm (.080") line. Heavier-duty heads accept up to .095"–.105", which lasts longer in thick weeds but loads the engine more.
Quick comparison
| Trimmer head | Feed type | Thread | Max line | Typical price |
|---|---|---|---|---|
| STIHL AutoCut C5-2 (OEM) | Bump feed | M8 x 1.25 LH (direct fit) | 2.0 mm (.080") | $40–$50 (OEM) |
| Shakespeare Speed Feed 400 | Bump feed, fast reload | Adapters incl. (Stihl kit needed) | .095" | $25–$30 |
| Oregon 55-265 | Bump feed, speed load | 7/8/10 mm LH adapters incl. | .105" | $43–$75 |
| Husqvarna T25 | Tap advance (bump) | M8 / M10 / 3/8" versions | .095" | ~$30 |
| Opuladuo C5-2-compatible | Bump feed | M8 x 1.25 LHF (direct fit) | 2.0 mm (.080") | $25.99 |
Prices are typical US street prices observed at major retailers; they move around, so check the current listing.
1. STIHL AutoCut C5-2 — the OEM reference (part 4006 710 2106)
This is the head STIHL itself sells for the FS45, and the benchmark everything else is measured against. It threads straight onto the FS45's M8 x 1.25 left-hand shaft with no adapter, runs 2.0 mm line, and advances with a bump. Fitment is officially listed for the FS38, FS40, FS45, FS46, FS50, FSE60, FSE71, and FSE81.
Pros: Guaranteed fit; simple, proven bump-feed mechanism; light head suits the FS45's power.
Cons: Highest price of the group at retail (~$40–50 for genuine OEM); aftermarket clones at $10–20 vary wildly in quality.
Best for: Owners who want zero fitment risk and don't mind paying OEM prices.
2. Shakespeare Speed Feed 400 — fastest reload
The Speed Feed 400 (Echo part 99944200907) is the forum favorite for one reason: you reload line in under a minute without taking the head apart. Owners on lawn and equipment forums call it the best head they've owned. For a Stihl, you'll need Echo's Rapid Loader adapter kit — forum users with an FS45 report using the Stihl-specific bushing from the kit, so confirm whether your shaft needs the curved- or straight-shaft adapter before ordering.
Pros: Fastest line changes of any head here; takes up to .095" line; well under $30.
Cons: Adapter required for Stihl (extra part to get right); a few users report occasional bump-feed hiccups where line retracts and the head must be reopened.
Best for: Anyone who hates restringing and trims often enough for reload speed to matter.
3. Oregon 55-265 — the heavy-duty pick
Oregon's 4-1/2" speed-feed head ships with three left-hand adapters (7 mm x 1.0, 8 mm x 1.25, 10 mm x 1.25), so the FS45's M8 x 1.25 LH thread is covered out of the box. It holds 15 feet of .095" line and accepts up to .105", making it the best choice here for thick, overgrown areas. It's made in the USA and carries a limited lifetime warranty.
Pros: Adapters included — no separate kit to buy; largest line capacity; warranty.
Cons: The priciest aftermarket option (often $43–75 depending on retailer); bigger and heavier than the OEM head.
Best for: Overgrown lots and buyers who want the maximum line diameter.
4. Husqvarna T25 — the cross-brand option
Husqvarna's Tap Advance head is a well-regarded bump-feed unit with a split spool that resists tangling, sold in M8, M10, and 3/8" versions for around $30. One caution: Husqvarna lists it for Husqvarna trimmers, not the FS45. The M8 version matches the FS45's thread diameter on paper, but thread direction and fit are not manufacturer-verified for Stihl — check your thread size and direction before ordering.
Pros: Good spool design; competitive price; widely available.
Cons: No official Stihl fitment — strictly a check-first option.
Best for: Multi-brand households that already run Husqvarna gear and can verify fitment.
5. Opuladuo C5-2-compatible trimmer head — best value pick
Opuladuo's head is built as a direct replacement for the STIHL C5-2 (part 4006 710 2106 / 4006 710 2103), with an M8 x 1.25 LHF threaded arbor that fits the FS45 with no adapter. The product page lists 26+ compatible Stihl models including the FS38, FS40, FS40C, FS45, FS45C, FS46, FS50, and FSE60, at $25.99 — roughly half the price of one OEM head.
Opuladuo C5-2-compatible trimmer head (4006 710 2106) (actual product photo).
Pros: Direct OEM-spec fit (M8 x 1.25 LHF); about half the OEM price; fitment list printed on the product page.
Cons: Aftermarket brand — buy it for the fitment spec, which is printed on the product page, not for the STIHL name.
Best for: FS45 owners who want the OEM fit at aftermarket money.
What FS45 owners actually say
A few real notes from owner forums — linked so you can read the full threads:
- Speed Feed 400 on the FS45: An FS45 owner on Lawn Mower Forum confirms the Echo Speed Feed 400 ships with the Stihl adapter and fits his saw — with the caveat to match the straight-shaft vs. curved-shaft kit. Other owners in the same thread call it the best head they've owned; one honest dissent reports line occasionally retracting into the hub. (Lawn Mower Forum thread)
- Which adapter, exactly: On BobIsTheOilGuy, an FS45 (curved shaft) owner tracked down the precise piece needed for the Speed Feed 400 — the 10 mm x 1.0 mm LH bushing — and another member identified Echo's Rapid Loader Adapter Kit (p/n 215-60057), labeled for Stihl FS/FE curved-shaft trimmers. (BobIsTheOilGuy thread)
FAQ
What thread size does the Stihl FS45 trimmer head use?
M8 x 1.25 left-hand thread. Any replacement head must match this directly or through an included adapter.
Will a Speed Feed 400 fit my Stihl FS45?
Yes, with Echo's adapter kit for Stihl. Owners report needing the Stihl-specific bushing — verify whether your FS45 needs the curved- or straight-shaft adapter in the kit.
Bump feed or auto feed — which is better for the FS45?
Bump feed. It's simpler, wastes less line, and every head on this list uses bump feed — the FS45's stock setup is bump feed, and there's no reason to change.
What line diameter should I run?
2.0 mm (.080") is the stock size. If you upgrade to the Speed Feed 400 or Oregon 55-265, you can step up to .095" for thicker weeds.
Bottom line
Want zero risk? Buy the STIHL AutoCut C5-2. Want the fastest reloads? Get the Speed Feed 400 with the Stihl adapter kit. Want the best price for a guaranteed FS45 fit? Opuladuo's C5-2-compatible trimmer head matches the OEM M8 x 1.25 LHF spec at $25.99.
Disclosure: Opuladuo sells a compatible trimmer head; this article compares it alongside major brands. Specs above come from manufacturer listings and retailer product pages; compatibility claims are limited to what each product page states — when in doubt, check your thread size before ordering.
By the Opuladuo Parts Team — last updated October 8, 2026.
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