The main difference between MR11 and MR16 are as follows:

1. Size The MR-16 bulbs diameter is 2 inch (50mm)
   The MR-11 bulbs diameter is 1.375 inch (35mm)

2. Base the most common base for MR16 bulbs is GU5.3 or GX5.3 base - 2 pin base with 5.3mm between pins the most common base for MR11 bulbs is GU4 - 2 pin base with 4mm between base