What you need.

SAE – Conduit pipes 1/2 inch diameter 0.7 inch/17.8mm OD:

METRIC – Metal Pipes with OD 17.8-18.5mm:

Part200x300x200 build300x300x300 (1 CF) build400x400x400 build500x500x500 build
Base front along X axis385mm485mm631mm777mm
Base back along X axis367mm467mm613mm759mm
Base along Y axis400mm426mm526mm627mm
Y rails477mm503mm603mm703mm
X rails477mm577mm723mm869mm
Z rails427mm527mm627mm727mm
Top along X axis385mm485mm631mm777mm
Z support446mm552mm658mm764mm
Lead screw length version 1420mm+510mm+610mm+710mm+
Lead screw length version 2410mm+500mm+600mm+700mm+

Other parts:

SAE:

FastenerQuantitiesPart example link
5/16 1 inch bolts23
5/16 1.5 inch bolts10
5/16 nuts33
#6 3/4 screws40
#6 1/2 inch screws22
#6 nuts62
#10 1 inch screws for pulleys2
#10 nuts2
M3 8-10mm bolts for NEMA motors16

METRIC:

FastenerQuantitiesPart example link
M8 25mm Bolts23
M8 40mm bolts10
M8 Nuts33
M4 20mm bolts40
M4 12mm bolts22
M5 25mm screws for pulleys2
M5 nuts2
M3 8-10mm bolts for NEMA motors16

For both SAE and Metric:

PartQuantitiesPart example link
For the printer frame:
608 ball bearings35608
Idler Pulley 20 teeth 5mm ID2Idler Pulley
GT2 beltbelt
End stop sensors3sensor
GT2 Timing Belt Pulley 5mm Bore 6mm Width2Motor Pulley
Nema 17 motors4
RAMPS 1.4 board1ramps 1.4
Arduino board1arduino
driver board A4988 or DRV88254A4988
DRV8825
12V PSU1PSU
40 mm fan1fan
For Extruder:
Nema 17 motors1
608 ball bearings2
5/16 2 1/2 inch bolt for lead screw1
5/16 nuts2
Extruder head1head