These are the 6.5mm High Current Bullet Connectors from Castle Creations.
FEATURES: Gold plated Fits wire diameter up to 6.5mm Use 13-8 gauge wire Up to 200A current
INCLUDES: Three sets of bullet connectors
REQUIRES: Solder and soldering iron - HCAR0776 and STAR2000
SPECS: Length: .59" (15mm) Inside diameter: .15" (4mm) (where the wire is soldered to) Outside diameter: .25" (6.5mm)