Objectives: This MIS proposes an interactive tutorial session where ISMRM attendees will reassemble two open-source Halbach ultra-low-field 50mT preclinical MRI magnet similar to the system built at the Imaging Without Borders (IMAGINE) Summer School in Canada and South Africa [1]. They will also rebuild two open-source field-mapping robots, use them to remap the magnet’s homogeneity, and learn how this and other components (RF, gradients, electronics, acquisition console) come together in an ultra-low-field scanner. Significance: This session builds on the 2025 ESMRMB Hands-on Low-Field MRI with CAMERA Workshop [2] and offers the MRI community a unique opportunity to learn ultra-low-field MRI magnet design, components, engineering/construction, and performance testing, at ISMRM. Specifically, the session will follow the train-the-trainer approach piloted at ESMRMB to teach and demystify MRI engineering, while exposing curious learners to fundamental concepts of MRI hardware, through experiential learning. More importantly, the MIS will explore the reusability of the ESMRMB-IMAGINE MRI Education (ERNIE) toolkit – an open-sourced 80mm 50 mT Halbach mice-like scanner with field-map robot, designed as a cost-effective and sustainable teaching tool in any settings (high- to low-resourced). Content: The tentative program proposed below, will be a condensed workshop, with focus on teaching reproducible open-source assembly practices and field mapping – crucial to ensuring harmonized MR systems. The session will include a keynote lecture on ultra-low-field MRI engineering and application concepts from an expert speaker who will share lessons learned from participating in many types of open-source onsite constructions around the world (Uganda, Singapore, Cape Town, Montreal, etc.,). Based on our ESMRMB workshop experience [2] with 59 participants, our trainers (IMAGINE Summer School Alums) guided attendees to complete ERNIE’s onsite construction and successfully mapped its field within 1.5h. Given, expected increase in ISMRM attendance, we anticipate that two ERNIEs will be completed in record time during the session. Our timed-participation technique will give attendees the opportunity to be part of the reassembly and field remapping process. We will compare live at the session, the ESMRMB field map to ISMRM field maps, and field maps obtained in the low-field lab at the Montreal Neurological Institute. We will also obtain participant feedback and work with the ISMRM Low-Field and Reproducibility Study Groups to share the toolkit design, software codes, materials, and how-to-guides to democratize its dissemination widely. Proposed 2-hr agenda: 1) Welcome and Tutorial Instructions (5 mins), Keynote Presentation (20 mins), ERNIE Build Guide (10 mins), Onsite Reassembly (1hr), Field remapping (20 mins), Wrap-up and Reflections (5min). [1] https://event.fourwaves.com/imagine [2] https://github.com/CAMERA-MRI/IMAGINE