Roundel 

Rondle, Roundle, Roundlet

Roundels are subordinaries in the form of a circle, each possessing a distinctive title which is sufficient in blazoning to denote its tincture. They are of two sorts. Metal roundels are drawn flat whereas those in colour are represented as spherical or concave. A spherical roundel is also termed ball

They are:

Bezants - Or  (The ancient gold coin of Byzantium)

Fountain or Syke  - represented by wavy lines drawn fess-wise alternately Argent and Azure.

Golpes, (Wound)  - Purpure

Guzes - Sanguine 

Hurtes - Azure

Oranges  - Tenné

Pellets   - Sable  - Also termed Bullet,  Gunstone, Gunshot or Ogress

Plates - Argent

Pomme  (Pl. Pomeis)   - Vert

Syke or Fountain - represented by wavy lines drawn fess-wise alternately Argent and Azure

Torteaux   - Gules

Roundels may also be composed of any of the furs or divided into equal tinctures when they are blazoned a roundel ermine or a roundel checky or and gu. Roundels were sometimes termed Gastells in ancient works. See Subordinary