This box of 10 inserts fit all Byrd Shelix heads.

Size = 15mm  x 15 mm x 2.5 mm

Solid Carbide 

edges :  sharp points with edges with a 100mm radius  (place edge on table and you should see a little light on each end, they should rock slightly)

Plastic Case Includes  10 knives

Genuine Byrd Inserts from Byrd.

SHELIX Insert Replacement from Brett Byrd on Vimeo.