Fitbit air adapter for Bicep straps or NATO bands

This is a continuation following comments from the original model that only have band loop on one side.

This model has loops on both side for more secure wearing and compatibility with standalone NATO bands and Arm/Bicep Straps.

Variations:

• nato-XXmm: one piece without swivel, with holes on both ends with XXmm x 3.5mm opening. 
  • where XX is one of 18, 20, 22, 24
• double-sides-swivel-XXmm: print-in-place swivel loops on both sides with XXmm x 4mm opening.