T4 bulb- G8 vs. GY8.6 base

[Part 77]

Who is a miniature bulb guru?
I'm dealing with under cabinet fixtures (120 volt) that are labeled "Max. 35 watt type T4 lamp".
I have seen 2 blister packs of halogen lamps with what both appear the same, except one is marked G8 base and one is marked GY8.6 base. What is this base spec referring to (I suspect a milimeter measurement)?
Are halogen versions of a 120 volt T4 lamp dimmable? TIA.

 

[LarryFine]

From the pics I Googled, the bulbs look the same. The latter might have thicker pins.

As far as I know, all halogens are incandescent, and therefore, dimmable.

 

[zapped3]

I have seen 2 blister packs of halogen lamps with what both appear the same, except one is marked G8 base and one is marked GY8.6 base. What is this base spec referring to (I suspect a milimeter measurement)?

I bought a bulb for my microwave that didn't fit. I'm no expert but after I googled GY8.6 and found this thread that didn't answer my question, or the the same as the question#1 of the original poster. I went to Wikipedia and searched GY8.6 and without even going to the article on "Incandescent bulbs" the search excerpt is as follows.
"Some common sizes include ...G8 (8 mm), GY8.6 (8.6 mm)..."
The GY8.6 is too wide for my application. It is 8.6 mm (probably between center-lines) of the leads.