If you have spent any time browsing e-cigarette reviews on this site, you know that electronic cigarettes come in all shapes and sizes. One of the newest e-cigarettes on the market comes from one of the original ecig mod makers. The SD Keychain by Trog is an interesting hybrid of a stealth e-cigarette mod and standard electronic cigarette. The most notable thing about the SD Keychain is its diminutive size (and price). In the SD Keychain review that follows we’ll see if good things really do come in small packages.