IPSW Portal

Choose aProduct→Choose aPlatform→Choose aVersion→ClickDownload

Download 4.3.1 (15T5535b) for Apple Watch Series 3 (42mm, LTE)

Version:	4.3.1
Build:	15T5535b
Signed:	No
Size:	0.12 GB
Release Date:	2018-04-02 17:13:36
Upload Date:	2018-03-29 01:36:05

Secure download directly from Apple's servers