Assemble Watches
Seiko Mod Parts Planner
Assemble Watches is a free Seiko mod parts planner. Select compatible parts for your build, verify fitment automatically, and export a complete shopping list with vendor links — before you spend a pound.
Plan Your Build →Complete Seiko mod parts checklist
Every part below feeds into the Assemble Watches builder. Select each one and the tool checks compatibility as you go.
Case
Sets the diameter, lug width, and movement compatibility.
Movement
NH35 (no date) or NH36 (day/date) covers most builds.
Dial
Must match movement dial feet pattern (NH35-compatible for NH35 builds).
Hands
Hour, minute, and seconds. Hand tube sizes must match the movement pinion posts.
Bezel ring
Must match case diameter. Check finishing: polished vs brushed.
Bezel insert
Must fit the bezel ring. Aluminum, ceramic, or sapphire options exist.
Crystal
Must match case crystal diameter. Mineral or sapphire. Check thickness too.
Caseback
Often comes with the case. Ensure correct thread pattern for your case brand.
Bracelet or strap
Must match lug width (typically 20mm for SKX007/SRPD platforms).
Crown and stem
Often overlooked. Check thread compatibility if replacing from the case kit.
Common questions
- What parts do I need for a Seiko mod build?
- A complete Seiko mod build requires: a case, movement (typically NH35 or NH36), dial, hands, bezel ring, bezel insert, crystal, caseback, and bracelet or strap. Each part has specific compatibility requirements with the others — Assemble Watches checks these automatically.
- How do I know if Seiko mod parts are compatible?
- Key compatibility checks: dial feet must match your movement (NH35 or NH36), hand tube sizes must match the movement pinion posts, crystal diameter must match the case, and lug width must match your bracelet or strap. Assemble Watches automates all of these checks as you build.
- Where can I build a Seiko mod parts list online?
- Assemble Watches (assemble.watch/build) is purpose-built for this. Select your parts, get automatic compatibility checking, then export a complete parts list with links to trusted vendors. Free, no account required.
- What is the difference between NH35 and NH36?
- Both movements are identical in case footprint, hacking, hand-winding, and beat rate (21,600 bph). The NH36 adds a day display alongside the date. Choose based on whether your dial has a date-only or day/date window. Most NH35-compatible dials and hands also fit the NH36.