This is a professional grade splice kit. 

This is what you need if doing the job once is important to you.

 Kit Contains: 

(3) Blackburn CS85 2/0 Aluminum Sleeves (BG or 5/8 die).

(1) Blackburn CS68 #4 Aluminum Sleeves (BG or 5/8 die).

(4) Raychem WCSM 24/6 Heavy Wall adhesive lined heat Shrink Tubing Range .25" to .64" (6.5 to 16.5 mm) 9" (225mm) Long

 Special Tools Needed:

Clean Burning Torch or Heat Gun 

Compression Tool with 5/8","G" or "BG" die

I have Underground Aluminum  splice kits available for wire sizes from #6 thru 4/0 I also have the components available separately. If you can not find what you need feel free to ask.