Absolute Optical encoders are available with solid or hollow shafts.

Encoder	Shaft type	Shaft sizes	Output code	Protection
MH58	hollow	10 mm 12 mm	binary Gray	IP65
MV58	solid	6 mm 10 mm	binary Gray	IP65
SV58	solid	6 mm 10 mm	binary Gray Excess-Gray	IP65
WK02/1	hollow	16 mm 20 mm	binary Gray	IP54 IP65
WK50/1	hollow	16 mm 20 mm	binary Gray	IP54 IP65