Ask five suppliers what colour a 1/8" horseshoe shim is and you will get more than one answer. There is no ASTM standard for shim colour, no industry agreement, nothing. Each manufacturer picked a scheme and kept it.
That matters on a job. A crew that learned colours on one brand will grab the wrong gauge from another brand's box without stopping to measure — which is the whole reason colour coding exists.
Quick answers
Is there a standard colour code for horseshoe shims?
No. There is no ASTM standard and no industry agreement; every manufacturer uses its own colours, so check the gauge, not the colour, on an unfamiliar box.
What colour is each gauge in our boxes?
1/16" is blue, 1/8" is red, 1/4" is black and 1/2" is brown. All four are 3" x 4" with a 7/8" bolt hole, 1,000 to the box.
How can I check shim thickness without a caliper?
Stack ten. Ten 1/16" shims make 5/8"; ten 1/8" shims make 1-1/4".
Our chart
| Thickness | Colour | Per box |
|---|---|---|
| 1/16" | Blue | 1,000 |
| 1/8" | Red | 1,000 |
| 1/4" | Black | 1,000 |
| 1/2" | Brown | 1,000 |
All four are 3" x 4" with a 7/8" bolt hole, one gauge to the box, so nothing gets mixed in the van.
How to check a box you did not buy from us
Do not trust the colour. Trust the caliper, or failing that, a stack: ten 1/16" shims make 5/8", ten 1/8" make 1-1/4". If a box has no gauge printed on it and you cannot measure, treat it as unknown — a shim that is one step thinner than you think will let a frame settle out of square.
What the shim is for
Plastic, because plastic does not do what the alternatives do. Wood absorbs water and rots, and it crushes under sustained load. Steel rusts and stains the frame. Plastic does neither, and every shim in a box is the same thickness — which is the thing you actually rely on when you are shimming a long run of storefront and want the head straight.
The open slot is the point of the horseshoe shape. It slides in around a bolt or anchor that is already in place, so nobody has to back the fastener out to correct a gap.
Where it goes
A permanent shim should sit entirely inside the joint, behind the finish materials, and it must not foul the sealant. If a shim is proud into the joint the bead gets a hard point in it and that is where it will split.
Not the same as a U shim
U shims are a different line: 1-1/2" x 2" with a 1/2" bolt hole. The two are not interchangeable — a 1/2" slot will not go round a 7/8" anchor. If you are not sure which your anchors take, measure the anchor, not the shim.
U shims are not listed on the site at the moment. We can still supply them — ask us with the gauge and the quantity.
See the horseshoe shims · The shim range · Horseshoe or U shim?