How to Replace a CRAFTSMAN CMZST065 Spool (CMCST900 Trimmer)

The CMZST065 is CRAFTSMAN’s pre-wound replacement spool for its 20V trimmer/edgers. The CMCST900 manual says the trimmer uses 0.065” (1.65 mm) round nylon line only — no serrated or heavier line, which overloads the motor. The steps below follow “Replacing Spool Assembly” in the CMCST900 instruction manual (page 8).

Steps, as CRAFTSMAN writes them

1. Remove the battery from the trimmer.
2. Press the release tabs on the spool cap and remove the cap from the spool housing.
3. For best results, CRAFTSMAN says to replace the spool with CMZST065.
4. If the lever in the base of the housing comes loose, put it back in the correct position before inserting the new spool.
5. Clean dirt and grass from the spool cap and spool housing.
6. Unfasten the end of the line and guide it into the eyelet.
7. Push the new spool onto the boss in the housing and rotate it slightly until it is seated.
8. About 5-3/8” (136 mm) of line should stick out of the housing.
9. Line up the release tabs on the cap with the slots in the housing.
10. Snap the cap back on — press the release tabs and push it into the housing until it snaps securely into place.

The manual adds: make sure the cover is fully in place and listen for two audible clicks, one for each release tab. Then power the trimmer on — within a few seconds you should hear the line being cut to the right length automatically.

Two warnings from the manual: take care the line doesn’t get trapped under the spool, and don’t bump the trimmer on the ground to feed line — this head feeds automatically. If the line reaches past the trimming blade, cut it back so it just reaches the blade.

Which trimmers take the CMZST065

CRAFTSMAN lists the CMZST065 (single spool) and CMZST0653 (3-pack) for the CMCST900, CMESTA900, CMESTE920 and CMCST98020. The replacement cap is the CMZST120SC. The CMCST910 uses the .080” CMZST080 / CMZST0803 spools instead — see the spool finder.

Refilling with bulk line

The same manual allows rewinding the spool with bulk 0.065” round line: fold about 3/4” (19 mm) at the end of the line, feed it into one of the anchoring slots, wind neatly in layers in the direction of the arrow on the spool — no criss-crossing — and cut the line when it reaches the recesses. Our winding guide covers the technique.

Sources: CRAFTSMAN CMCST900 20V MAX String Trimmer/Edger instruction manual (NA473221, 10/23), “Replacing Spool Assembly” and “Rewinding Spool from Bulk Line”, p. 8 (PDF, Stanley Black & Decker service site); CRAFTSMAN product pages for the CMZST065, CMZST0653 and CMZST120SC cap. Checked September 25, 2026.