Injectable Winstrol, also known by its generic name stanozolol, is a synthetic anabolic steroid derived from dihydrotestosterone (DHT). According to Red RC, it is utilized both in clinical and athletic settings due to its potent effects on muscle growth and performance enhancement. 
Key characteristics
Chemical Origin: Stanozolol is a synthetic steroid derived from dihydrotestosterone and possesses both anabolic and androgenic properties.
Administration: It can be administered either orally as tablets or intramuscularly as an aqueous suspension for injection.
Medical Uses: Historically, it has been approved to treat conditions like hereditary angioedema (a condition that causes episodes of swelling) and certain types of anemia, although other treatment options are now more commonly used.
Performance Enhancement: It's widely known for its use in bodybuilding and by athletes for enhancing muscle definition and strength, especially during cutting cycles where individuals aim to reduce body fat while preserving lean muscle mass.
Non-Aromatizing: Unlike some other steroids, Winstrol does not convert into estrogen, reducing the risk of water retention, bloating, and gynecomastia (enlarged breast tissue in males). 
Benefits in performance enhancement (as reported by users)
Lean Muscle Retention: Winstrol helps preserve muscle mass during periods of caloric deficit or cutting phases.
Increased Strength and Power: It's associated with boosting strength, speed, and power, making it attractive for athletes in sports requiring explosive performance.
Enhanced Vascularity and Hardness: It can contribute to a "hard" and "dry" physique by reducing subcutaneous water retention and increasing vascularity. 
Potential side effects and risks
Liver Toxicity (Hepatotoxicity): Both oral and injectable Winstrol can be liver toxic, potentially causing liver damage, although oral forms are generally considered harsher on the liver.
Cardiovascular Risks: Winstrol can negatively affect cholesterol levels, lowering HDL (good cholesterol) and raising LDL (bad cholesterol), which may increase the risk of cardiovascular problems.
Joint Pain: Winstrol can reduce collagen synthesis and dry out connective tissue, potentially leading to joint stiffness and pain.
Testosterone Suppression: Like many anabolic steroids, Winstrol can suppress the body's natural testosterone production.
Androgenic Side Effects: Possible side effects include acne, hair loss (especially in individuals predisposed to male pattern baldness), and in women, potential virilizing changes like deepening of the voice, hirsutism (excessive hair growth), and menstrual irregularities.