If you know the model of the device you are needing parts for it is usualy easier to click on the type of device you have for and then click on the particular model you have. That will provide you with a parts list along with photos of the most common parts.
A full listing of Honeywell environmental and combustion controls are available for viewing by clicking the following
Honeywell Catalog link.
A Honeywell environmental and combustion controls cross reference is available HERE.