These 90 mm, felt-lined mounting rings are made from solid aluminum, black-anodized, and will fit all William Optics 80 and 90mm telescopes and most other 90 mm OD tubes.   

A worthwhile investment.

• Supplied with five threaded holes (external imperial threading 1/4x20; internal M6 metric threading) for mounting on most dovetail plates and WO dovetail plate.
• Equally holed on top to fit additional accessories.
• Nice comfortable knobs with teflon paint protection on locking end.
• Felt-lined to protect even the most delicate telescope finish.