Specifications:

Material:aircraft aluminum T6061
Finish:Black anodized
Features:
Quad Rail Handguard
Fits .223/5.56 (AR15) Spec
Free Floating Quad Rail Mounting System
Free float design, allowing for direct mount to the receiver
Picatinny on all 4 rails  （21mm)
Very easy to install (tool included)
Hard anodized finish
Barrel nut inside hole diameter: 1.02 in (26mm)
Barrel nut outside diameter: 1.84 in (46.83 mm)
Barrel nut mounting thread spec.: 1-1/4-18 UNC

Package:
One quad rail+barrel nut + jam nut+wrench

Model:  M16-4
Dimensions 4" (length) x 2.5" x 2.5" (width)
Weight : 205g
# of Slots
8 on the top rail
6 on the side and bottom rails

Model:  M16-7
Dimensions 7" (length) x 2.5" x 2.5" (width)
Weight : 300g
# of Slots
14 on the top rail
12 on the side and bottom rails

Model:  M16-10
Dimensions 10" (length) x 2.5" x 2.5" (width)
Weight : 420g
# of Slots
24 on the top rail
22 on the side and bottom rails

Model:  M16-12
Dimensions 12" (length) x 2.5" x 2.5" (width)
Weight: 450g
# of Slots
29 on the top rail
27 on the side and bottom rails

Model:  M16-15
Dimensions 15" (length) x 2.5" x 2.5" (width)
Weight : 500g
# of Slots
36 on the top rail
35 on the side and bottom rails