AXA Equitable has a guaranteed interest TSA account. What investment vehicles are used to provide that income.

AXA Equitable also offers investment grade bonds as a TSA investment vehicle. How does the investment grade bonds compare to the guaranteed interest TSA account? Which is a safer retirement vehicle? How do they compare? What are the pros and cons of each?

I answered part of this on previous question. Safer retirement vehicle in term of not losing what you put in when you are alive would be guaranteed interest TSA. Most TSA has a stepped up cost which guaranteed when you died your beneficiaries won't get worse than the principal or the amount on that anniversary date, whichever is higher.
Be aware of the inflation which will eat away most of your interest if you invest in the guaranteed interest. Consider the cost of gas and stamps as an example of inflation.

The Guaranteed Interest Account provided by insurance companies in their annuity and life insurance products is not directly tied to specific investments. Typically, an insurance company invests its own assets fairly conservatively, meaning government and corporate bonds and derivatives. Based on the current and projected performance of their own investments as well as the company's profitability, the insurance company will declare the crediting interest rate on their Guaranteed Interest Account annually. That means the rate can and typically will change from year to year. In the fine print of the prospectus there will be a guaranteed minimum rate that the declared rate will never fall below. Read your prospectus or talk to the representative that services your employer to get the details on the AXA/Equitable product.