Bicep grip heel hook
Here is a nice variation of the standard heel hook grip.
Caleb has opened Cassie's guard by pushing her right thigh down with his left forearm.
Caleb slides his left knee inside his left arm onto Cassie's thigh
On the other side, Caleb steps up with his right knee close to Cassie's left hip
Caleb steps his right foot over Cassie's left hip and falls back making sure her leg stays bent, he closes his right arm around Cassie's left ankle
Caleb sits up and reaches his left forearm under Cassie's left heel
Caleb grabs his right bicep with his left hand
Caleb grabs his head with his right hand. To finish the submission, Caleb uses his legs to keep Cassie's knee bent, and leans back and to the left to apply the heel hook