OWC DIY Kit for all Apple iMac 2011 for replacing the main hard drive
Amazon | 【国内正規品】OWC DIY Kit for all Apple 21.5" iMac 2011 Models for installing an internal SSD. Without tools. (対応機種:iMac 21.5インチ 2011) | OWC | PCパーツ 通販
iMac Intel 21.5" and 27" (Mid 2011) SSD Upgrade Bundle - iFixit Store