Basic Flat Shoe Inserts / Insoles / Filler

I needed 3mm flat inserts for a pair of boots to fill space under other third-party insoles.

I made these and sized them to match the original inserts. Paired with the new insoles, the boots are a great fit. Now that I've started this, I have some other footwear to customize :).

I printed in TPU 95A at high speed, with no top or bottom shell layers and 20% honeycomb infill. If you are happy enough with the cushion of whatever insoles you pair these with, PETG might be a good choice too.

If the model hangs off your print area to start, I recommend setting your size first. Then, if needed, rotate the model 45° to accommodate larger sizes as needed.

To adjust size:

Measure your reference inserts (or refer to the chart below).
- Per the tables below, STL is about US size 12 or EU 45. My boots didn't match this at all, so make sure to measure the footwear you actually are using.
Scale X and Y to match your needed width and length. STL is 94 x 287mm.
Recheck that your Z size matches what you want as well. STL is 3mm thick.

To adjust pattern and density:

Set top shell layers and bottom shell layers to your preference. Set to zero if you want open mesh.
Set your infill pattern and percentage to your preference.

Consider the use of modifiers if you would like to adjust the density for a specific part of the footbed. You can use basic shapes, or the instep files here.

Size References:

The tables below are from this page.

Their metric conversions are imprecise, so this tool or similar may be useful.

Men’s insole size chart

US Sizes	Euro Sizes	UK Sizes	Inches	CM
6	39	5.5	9.25	23.5
6.5	39	6	9.5	24.1
7	40	6.5	9.625	24.4
7.5	40-41	7	9.75	24.8
8	41	7.5	9.9375	25.4
8.5	41-42	8	10.125	25.7
9	42	8.5	10.25	26
9.5	42-43	9	10.4375	26.7
10	43	9.5	10.5625	27
10.5	43-44	10	10.75	27.3
11	44	10.5	10.9375	27.9
11.5	44-45	11	11.125	28.3
12	45	11.5	11.25	28.6
13	46	12.5	11.5625	29.4
14	47	13.5	11.875	30.2
15	48	14.5	12.1875	31
16	49	15.5	12.5	1.8

Women’s insole size chart

US Sizes	Euro Sizes	UK Sizes	Inches	CM
4	35	2	8.1875	20.8
4.5	35	2.5	8.375	21.3
5	35-36	3	8.5	21.6
5.5	36	3.5	8.75	22.2
6	36-37	4	8.875	22.5
6.5	37	4.5	9.0625	23
7	37-38	5	9.25	23.5
7.5	38	5.5	9.375	23.8
8	38-39	6	9.5	24.1
8.5	39	6.5	9.6875	24.6
9	39-40	7	9.875	25.1
9.5	40	7.5	10	25.4
10	40-41	8	10.1875	25.9
10.5	41	8.5	10.3125	26.2
11	41-42	9	10.5	26.7
11.5	42	9.5	10.6875	27.1
12	42-43	10	10.875	27.6

Kid insole size chart

US Sizes	Euro Sizes	UK Sizes	Inches	CM
5.5	21	4.5	5	12.7
6	22	5	5.125	13
6.5	22	5.5	5.25	13.3
7	23	6	5.5	14
7.5	23	6.5	5.625	14.3
8	24	7	5.75	14.6
8.5	25	7.5	6	15.2
9	25	8	6.125	15.6
9.5	26	8.5	6.25	15.9
10	27	9	6.5	16.5
10.5	27	9.5	6.625	16.8
11	28	10	6.75	17.1
11.5	29	10.5	7	17.8
12	30	11	7.125	18.1

Youth insole size chart

US Sizes	Euro Sizes	UK Sizes	Inches	CM
12.5	30	11.5	7.25	18.4
13	31	12	7.5	19.1
13.5	31	12.5	7.625	19.4
1	32	13	7.75	19.7
1.5	33	14	8	20.3
2	33	1	8.125	20.6
2.5	34	1.5	8.25	21
3	34	2	8.5	21.6
3.5	35	2.5	8.625	21.9
4	36	3	8.75	22.2
4.5	36	3.5	9	22.9
5	37	4	9.125	23.2
5.5	37	4.5	9.25	23.5
6	38	5	9.5	24.1
6.5	38	5.5	9.625	24.4
7	39	6	9.75	24.8