As previously reported by ESPN NFL Insider Adam Schefter, Spikes signed a one-year deal worth $3.25 million.
According to documents filed with the NFLPA, Spikes' deal includes a $900,000 signing bonus, which is the only guaranteed money included in the deal.
Beyond that, Spikes has a $1.25 million base salary and a $850,000 roster bonus.
Here's how that roster bonus breaks down: Spikes will receive $53,125 per game that he is active. That gives the Bills some protection in the event of injury.
Spikes has shown some vulnerability to injury. Over the first four seasons of his career, he's played in 16 games just once -- last season. Even then, Spikes nursed a knee injury for much of the season.
The final $250,000 of Spikes' $3.25 million cap hit are likely-to-be-earned incentives.