Jaeger-LeCoultre Master Ultra Thin

Most Jaeger-LeCoultre Master Ultra Thin references take a 21 mm watch strap: 44 of 103. The lug width follows the case size: 34 mm case → 20 mm, 36 mm case → 17 mm, 39 mm case → 21 mm and 40 mm case → 20 mm.

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Jaeger-LeCoultre Master Ultra Thin lug width by case size

103 references measured. Updated 2026-10-29.

Case	Lug width	References	Watch strap attachment	For example
34 mm	20 mm	5	—	1252501, 1252520, 1258401
36 mm	17 mm	7	—	1242501, 1248420, 124842J
38 mm	20 mm	5	—	1342501, 13425SQ, 134350
39 mm	21 mm · 20 mm on 16 · 18 mm on 1	57	—	1212501, 1212510, 1218420
40 mm	20 mm · 21 mm on 4 · 18 mm on 3	22	—	1282510, 128255J, 128258S
41 mm	18 mm · 20 mm on 1	4	—	1332511, 1338421, Q1313581
42 mm	22 mm · 20 mm on 1	3	—	169241J, Q169242J

References that take a different watch strap

1263520: 20 mm, not the 21 mm of most 39 mm cases
1272501: 20 mm, not the 21 mm of most 39 mm cases
1272510: 20 mm, not the 21 mm of most 39 mm cases
1278420: 18 mm, not the 21 mm of most 39 mm cases
1292520: 20 mm, not the 21 mm of most 39 mm cases
12935E1: 20 mm, not the 21 mm of most 39 mm cases
1296520: 20 mm, not the 21 mm of most 39 mm cases
1303501: 20 mm, not the 21 mm of most 39 mm cases
1303520: 20 mm, not the 21 mm of most 39 mm cases
130354J: 20 mm, not the 21 mm of most 39 mm cases
13035E1: 20 mm, not the 21 mm of most 39 mm cases
1362510: 20 mm, not the 21 mm of most 39 mm cases
1363540: 20 mm, not the 21 mm of most 39 mm cases
13635E1: 20 mm, not the 21 mm of most 39 mm cases
1368430: 20 mm, not the 21 mm of most 39 mm cases
1378480: 20 mm, not the 21 mm of most 39 mm cases
Q1238480: 20 mm, not the 21 mm of most 39 mm cases
1152520: 18 mm, not the 20 mm of most 40 mm cases
1283501: 18 mm, not the 20 mm of most 40 mm cases
1288420: 21 mm, not the 20 mm of most 40 mm cases
1322410: 18 mm, not the 20 mm of most 40 mm cases
1682401: 21 mm, not the 20 mm of most 40 mm cases
1682410: 21 mm, not the 20 mm of most 40 mm cases
Q1682411: 21 mm, not the 20 mm of most 40 mm cases

And 2 more in the full list below.

Questions about the Jaeger-LeCoultre Master Ultra Thin

Do all Jaeger-LeCoultre Master Ultra Thin case sizes take the same watch strap?

No. The lug width changes with the case size: the 34 mm case takes 20 mm, the 36 mm case takes 17 mm, the 38 mm case takes 20 mm, the 39 mm case takes 21 mm and the 40 mm case takes 20 mm. Check your case diameter before you buy.

Can two Jaeger-LeCoultre Master Ultra Thin watches with a 39 mm case take different watch straps?

Yes. Of the 57 Jaeger-LeCoultre Master Ultra Thin references with a 39 mm case, 40 take 21 mm, 16 take 20 mm and 1 take 18 mm. The reference number decides, not the case size alone.