The Hitachi 711099 allows you to adjust the drill chuck by hand and tighten it without using a key. When used with an SDS+ drill you will be able to use conventional drill bits.
Please note you may receive either a Hitachi or HiKOKI 711099 adaptor. Both are the exact same item and serve the exact same purpose. The only difference is the branding on the packaging. HiKOKI is the new brand name for Hitachi.