From Forum Nokia Wiki

Java Technology for the Wireless Industry (JTWI) is a JCP specification (JSR 185) that defines what APIs must include a Java ME device platform after year 2003.

A JTWI device must include:

• MIDP 2.0
• WMA 1.1 (JSR 120)
• CLDC 1.0 (JSR 30)

Optional:

• MMAPI 1.1 (JSR 135)
• CLDC 1.1 (JSR-139)

It recommends some minimum requirements on device:

• 125x125 screen resolution
• 4096 colors (12 bits)
• 256Kb Java Heap Memory

An more recent evolution of this standard is Mobile Service Architecture.

Devices that implement JSR 185 should allow MIDlet JARs up to 64 KB, with application descriptors (JADs) up to 5 KB, and each MIDlet suite should be allowed to use up to 30 KB of persistent storage (RMS).