THE MAGAZINE IS not ASSEMBLED. YOU NEED TO REMOVE THE STANDARD METAL BASE PLATE AND REPLACE IT WITH THE CZ SP-01 BASE 0430177001. That will make a magazine that fits the CZ 75 Compact as shown in the picture below.

MEC-GAR CZ 75 COMPACT 9MM 16 RD EXTENDED MAGAZINE KIT MGCZ7516B/0430177001. CZ USED TO SELL A SIMILAR MAGAZINE, cz 11119 BUT THEY HAVE DISCONTINUED IT. 

FOR A MORE SECURE FIT YOU CAN USE THE THE LOCKING PLATE: MAGAZINE BASE LOCK SP-01/40P 75/85, SP-01, 97B/BD 0421176002. MOST JUST USE STANDARD LOCKING PLATE, THESE EXTEND FURTHER INTO THE BASE PAD. 

THIS IS A MEC-GAR CZ7516B 16 ROUND MAGAZINE WITH THE A CZ FACTORY CZ SP-01 BASE 0430177001. THE MAGAZINE IS NOT ASSEMBLED. YOU NEED TO REMOVE THE STANDARD METAL BASE PLATE AND REPLACE IT WITH THE CZ SP-01 BASE 0430177001. THIS WILL CREATE A MEC-GAR CZ 75 COMPACT 9MM 16 RD EXTENDED MAGAZINE MGCZ7516B/0430177001. THE MAGAZINE WILL FIT FLUSH IN THE CZ 75 9mm COMPACT, CZ P-01 AND CZ PCR PISTOLS. 

The magazine is also compatible in the Canik Shark-C, TRISTAR C-100, TriStar T100 and Canik 55 Stingray Compact.

When inserted the magazine will look like the magazine in the CZ P-06 below.