BOM for the Inline Filament Diameter Estimator (lowcost)

:::Printed parts:::
1 Block
1 Lever

preferably printed in PETG, ABS or ASA as PLA may creep significantly over time

:::Electronics:::
1 SMT control board (populated)
or
1 THT control board + components (see Eagle files)

Suitable programmer for ATTiny85 (eg USBtinyISP)

1 SS495A linear hall effect sensor (or comparable)

:::Fasteners:::
2 M3x8 screws (eg ISO 4762 M2x8)
1 3x24mm pin (eg DIN 7 3x24mm, for mating lever to the block)
1 3x16mm pin (eg DIN 7 3x16mm, for roller bearing in lever)
1 3x18mm pin (eg DIN 7 3x18mm, for idler bearing in block)
6 M3 threaded inserts

Pins may be replaced with screws or grubscrews, which may result in decreased precision

:::Mechanical / other:::
1 6x2mm magnet (eg N35)
4 623 bearings (preferably 623-2Z / 623-ZZ)
1 Ballpoint pen spring (or other soft 4mm spring)
Short length of PTFE tube

:::Calibration accessories:::
1 1.5mm drill bit
1 1.7mm or 1.8mm drill bit 
1 2mm drill bit
Calipers for verifying drill bit shaft diameter

Drill bits may be replaced with similar diameters. Measured diameter is to be written to firmware lookup table.