Bob's Knobs for Takahashi 225mm f/12 SCT Secondary: Precision Collimation Made Easy Effortless Collimation: Achieve precise collimation with Bob's Knobs tailored for Takahashi 225mm aperture f/12 Schmidt-Cassegrain telescope secondary mirrors. Part Details - Part: TSC225: Optimal Control: These black plastic knobs (13 mm diameter) with black anodized aluminum alloy threads provide easy and accurate collimation adjustments. Designed for TSC-225: Specifically crafted for Takahashi TSC-225 Schmidt-Cassegrain versions, ensuring a perfect fit. Dust Cover Compatibility: Keep your telescope protected; the factory dust cover seamlessly fits over these knobs. Streamlined Installation: The installation process is straightforward; the factory collimation screws' cosmetic cover must be removed and set aside, leaving the scope's operation unaffected. Experience hassle-free collimation and unlock the full potential of your Takahashi 225mm f/12 SCT with Bob's Knobs designed for the TSC-225 secondary mirror.