The SIG Sauer P225 is scaled down P220 chambered for 9mm with 8 rounds of ammunition in the magazine. The P225 is noticeably more compact than the P220, and was originally developed as the P6 for West German police forces in the 1970s, where it was introduced alongside the Walther P5 and the HK P7. The manual of arms between the P220 and the P225 is exactly the same.
The original version of the P225 was discontinued, but a new version called the P225-A1 was recently released by SIG a few years ago as the original P225’s successor. The new P225-A1 is essentially a single stack version of the P228/P229.