Durable U Packers for Precise Frame and Glazing Installations

U-shaped polypropylene packers (horseshoe shims) for precise frame and glazing installations. Colour-coded: 2mm yellow, 3mm red, 5mm green. Also available in mixed packs.

What are U packers?

U packers (horseshoe shims) are U-shaped plastic spacers used to level, plumb and align window frames, door frames and other components during installation. The U shape allows the packer to sit around a fixing screw or frame lug without needing to be removed when the screw is tightened. Available in 2mm (yellow), 3mm (red) and 5mm (green) — colour-coded for instant identification. Made from tough polypropylene that won't compress under sustained load.

How to choose the right U packer

For most window and door installations, 3mm (red) is the most commonly used size. Carry all three sizes (2mm, 3mm, 5mm) to handle any gap on site. Stack multiple packers for non-standard thicknesses — a 3mm + 2mm stack gives 5mm. Common applications include packing between the uPVC frame and structural opening, shimming behind hinge positions and lock keeps, packing behind battens for dry lining, and general construction levelling around fixings.
Trade Tip

Stack a 3mm + 2mm for 5mm packing with a tighter fit than a single 5mm packer.

Frequently Asked Questions

What sizes of U packer do I need?

For most installations, 3mm red is most common. Carry all three (2mm yellow, 3mm red, 5mm green) for any situation. Stack for custom thicknesses — e.g. 3mm + 2mm = 5mm.

Can U packers be used behind hinges?

Yes — this is one of the most common uses. When a door frame is slightly out of plumb, U packers behind the hinge positions correct the alignment. The U shape sits around the hinge screw without interfering.

Are U packers the same as horseshoe packers?

Yes. U packers, horseshoe packers, horseshoe shims and frame packers are all names for the same product — a U-shaped plastic spacer for frame levelling and alignment.