70mm Enclosed Spring Housing with 1kg or 1.5kg Lifting Force for Manual Windproof Roller Blinds

70mm Enclosed Variable Force Spring Housing, perfect matching for 70‑mm roller tube, core balancing component for manual zip‑track windproof roller blinds.

Housing is made of high‑strength engineering plastic with built‑in variable‑force spring steel core. Color‑coded for easy force identification: green housing stands for 1 kg lifting force, yellow housing stands for 1.5 kg lifting force. You can increase or decrease the number of spring units according to fabric weight and blind width to achieve perfect weight balance.

Different from traditional constant‑force springs, this variable‑force spring provides self‑adaptive torque throughout the whole up‑and‑down stroke. It avoids heavy pulling force when the blind is fully lowered and prevents sharp snap‑back during retraction. It delivers balanced, comfortable push‑pull feedback and enables the blind to hold position at any height, no free dropping or rapid rolling‑up.

The fully‑enclosed casing fully wraps the inner spring core, protecting it from dust, moisture and debris. It minimizes spring rust, internal jamming and force decay for longer service life. Easy to assemble, simply insert into 70 mm roller tube without complicated modification. Widely used for manual zip‑track windproof blinds on balconies, sunrooms, patios and outdoor courtyards.