Baader Protective Wide T-Ring System for the Canon EOS evolves the T-Ring 

• The 2" wide-aperture of the protective T-ring accepts 3 different attachment adapters, which are included with each T-ring:  Standard T-thread (42mm), 2" thin profile nosepiece, and 48mm thread (astro filter standard). 
• The internal filter compartment is able to accept both Baader 2" mounted filters, and 50.4mm diameter unmounted filters for the widest clear aperture possible (47.3mm aperture).
• The optimized design and tight manufacturing tolerances ensure the closest fit possible with the Canon EOS body.  This avoids the occurrence of focal plane tilt and image shift caused by play and wobble at this connection point.

The Baader Protective Wide T-Ring System includes 6 configurable parts:

• Protective T-ring Body
• Temperature Compensation Ring (for installation of 50.4mm x3mm unmounted filters)
• Adapter S52/M48 (for 48mm connection thread)
• T-thread/M48 adapter (for standard 42mm T-thread connection)
• S52/2" wide aperture 2" nosepiece (includes M48 filter thread)
• 1.5mm Allen Wrench