(1) Bucket Tappet / Cup Tappet Structure:
Cup-shaped or bucket cylindrical design, directly matched for overhead camshaft (OHC / DOHC) engines, the most common type for passenger vehicles.
Subtypes: Hydraulic bucket tappet, mechanical bucket tappet (including shim-over-bucket and shim-under-bucket types for manual clearance adjustment).
(2) Mushroom Tappet Structure:
Mushroom-shaped profile, mostly used in older OHV engines with an adjustment screw on top for valve lash.
(3) Cylindrical Tappet Structure:
Hollow cylindrical shape for weight reduction, widely applied in medium and large diesel engines / OHV engines, available in flat and roller versions.