MAILX vs. FSKLX

Last updated Jun 3, 2026

MAILX (BlackRock International Fund of BlackRock Series, Inc.) and FSKLX (Fidelity SAI International Low Volatility Index Fund) are both Foreign Large Cap Equities funds. Over the past 10 years, MAILX returned 7.96%/yr vs 5.84%/yr for FSKLX. A 0.78 correlation means they provide meaningful diversification when combined. MAILX charges 0.65%/yr vs 0.17%/yr for FSKLX.

Performance

MAILX vs. FSKLX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in BlackRock International Fund of BlackRock Series, Inc. (MAILX) and Fidelity SAI International Low Volatility Index Fund (FSKLX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, MAILX achieves a 11.69% return, which is significantly higher than FSKLX's 4.35% return. Over the past 10 years, MAILX has outperformed FSKLX with an annualized return of 7.96%, while FSKLX has yielded a comparatively lower 5.84% annualized return.

MAILX

• 1D: 0.73%
• 1M: 6.27%
• YTD: 11.69%
• 6M: 14.93%
• 1Y: 20.59%
• 3Y*: 11.91%
• 5Y*: 2.10%
• 10Y*: 7.96%

FSKLX

• 1D: -1.18%
• 1M: -1.18%
• YTD: 4.35%
• 6M: 6.52%
• 1Y: 8.36%
• 3Y*: 10.88%
• 5Y*: 5.50%
• 10Y*: 5.84%

*Multi-year figures are annualized to reflect compound growth (CAGR)

MAILX vs. FSKLX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
MAILX BlackRock International Fund of BlackRock Series, Inc.	11.69%	15.60%	0.46%	19.67%	-24.24%	9.32%	21.82%	31.77%	-21.45%	31.87%
FSKLX Fidelity SAI International Low Volatility Index Fund	4.35%	21.95%	1.20%	13.84%	-13.48%	9.91%	-1.57%	16.12%	-4.88%	21.40%

Correlation

The correlation between MAILX and FSKLX is 0.68, which is moderate. They share some common price drivers but move independently often enough to provide real diversification benefit when combined.

	Correlation
Correlation (1Y) Calculated over the trailing 1-year period	0.68
Correlation (3Y) Calculated over the trailing 3-year period	0.69
Correlation (5Y) Calculated over the trailing 5-year period	0.74
Correlation (10Y) Calculated over the trailing 10-year period	0.77
Correlation (All Time) Calculated using the full available price history since Jun 8, 2015	0.78

The correlation between MAILX and FSKLX has been stable across timeframes, ranging from 0.68 to 0.78 - a consistent structural relationship.

Return for Risk

MAILX vs. FSKLX — Risk / Return Rank

Compare risk-adjusted metric ranks to identify better-performing investments over the past 12 months.

MAILX

MAILX Risk / Return Rank: 24
MAILX Sharpe Ratio Rank: 24
MAILX Sortino Ratio Rank: 23
MAILX Omega Ratio Rank: 24
MAILX Calmar Ratio Rank: 21
MAILX Martin Ratio Rank: 25

FSKLX

FSKLX Risk / Return Rank: 11
FSKLX Sharpe Ratio Rank: 10
FSKLX Sortino Ratio Rank: 11
FSKLX Omega Ratio Rank: 10
FSKLX Calmar Ratio Rank: 12
FSKLX Martin Ratio Rank: 11

The rank (0–100) shows how this investment's returns compare to the risk taken. Higher = better. Based on the past 12 months of data, combining Sharpe, Sortino, and other metrics used by quantitative funds and institutional investors.

MAILX vs. FSKLX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for BlackRock International Fund of BlackRock Series, Inc. (MAILX) and Fidelity SAI International Low Volatility Index Fund (FSKLX). Risk-adjusted metrics are performance indicators that assess an investment's returns in relation to its risk, enabling a more accurate comparison of different investment options.

	MAILX	FSKLX	Difference
Sharpe ratio Return per unit of total volatility	1.43	0.88	+0.55
Sortino ratio Return per unit of downside risk	2.04	1.31	+0.73
Omega ratio Gain probability vs. loss probability	1.26	1.16	+0.10
Calmar ratio Return relative to maximum drawdown	1.71	1.18	+0.53
Martin ratio Return relative to average drawdown	6.38	3.29	+3.09
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

MAILX vs. FSKLX - Sharpe Ratio Comparison

The current MAILX Sharpe Ratio is 1.43, which is higher than the FSKLX Sharpe Ratio of 0.88. The chart below compares the historical Sharpe Ratios of MAILX and FSKLX, calculated using daily returns over the previous 12 months. A higher Sharpe Ratio indicates better risk-adjusted performance relative to the risk-free rate.

Sharpe Ratios by Period

	MAILX	FSKLX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	1.43	0.88	+0.55
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.12	0.48	-0.36
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	0.44	0.49	-0.06
Sharpe Ratio (All Time) Calculated using the full available price history	0.24	0.46	-0.22

Drawdowns

MAILX vs. FSKLX - Drawdown Comparison

The maximum MAILX drawdown since its inception was -59.57%, which is greater than FSKLX's maximum drawdown of -27.26%. Use the drawdown chart below to compare losses from any high point for MAILX and FSKLX.

Drawdown Indicators

	MAILX	FSKLX	Difference
Max Drawdown Largest peak-to-trough decline	-59.57%	-27.26%	-32.31%
Max Drawdown (1Y) Largest decline over 1 year	-12.34%	-8.64%	-3.70%
Max Drawdown (3Y) Largest decline over 3 years	-17.36%	-11.59%	-5.77%
Max Drawdown (5Y) Largest decline over 5 years	-41.68%	-24.99%	-16.69%
Max Drawdown (10Y) Largest decline over 10 years	-41.68%	-27.26%	-14.42%
Current Drawdown Current decline from peak	0.00%	-6.41%	+6.41%
Average Drawdown Average peak-to-trough decline	-16.14%	-5.14%	-11.00%
Ulcer Index Depth and duration of drawdowns from previous peaks	3.31%	3.09%	+0.22%

Volatility

MAILX vs. FSKLX - Volatility Comparison

BlackRock International Fund of BlackRock Series, Inc. (MAILX) has a higher volatility of 5.56% compared to Fidelity SAI International Low Volatility Index Fund (FSKLX) at 2.69%. This indicates that MAILX's price experiences larger fluctuations and is considered to be riskier than FSKLX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	MAILX	FSKLX	Difference
Volatility (1M) Calculated over the trailing 1-month period	5.56%	2.69%	+2.87%
Volatility (6M) Calculated over the trailing 6-month period	12.45%	7.95%	+4.50%
Volatility (1Y) Calculated over the trailing 1-year period	14.98%	10.62%	+4.36%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	17.87%	11.51%	+6.36%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	18.36%	11.94%	+6.42%

MAILX vs. FSKLX - Expense Ratio Comparison

MAILX has a 0.65% expense ratio, which is higher than FSKLX's 0.17% expense ratio.

Dividends

MAILX vs. FSKLX - Dividend Comparison

MAILX's dividend yield for the trailing twelve months is around 1.61%, less than FSKLX's 2.49% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
FSKLX Fidelity SAI International Low Volatility Index Fund	2.49%	2.59%	2.09%	2.31%	2.01%	2.42%	1.32%	6.06%	2.64%	1.69%	2.85%	1.10%
MAILX BlackRock International Fund of BlackRock Series, Inc.	1.61%	1.79%	0.90%	1.08%	1.13%	7.30%	0.33%	1.11%	1.83%	1.39%	1.62%	0.65%

Frequently Asked Questions

Can I hold both MAILX and FSKLX in my portfolio?

MAILX and FSKLX have a correlation of 0.68, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, MAILX or FSKLX?

MAILX has higher volatility (5.56%) compared to FSKLX (2.69%). In terms of maximum drawdown, MAILX dropped -59.57% vs FSKLX's -27.26%.

Which has better risk-adjusted returns?

MAILX currently has the higher Sharpe Ratio (1.43 vs 0.88), meaning it's delivered slightly more return per unit of risk over the trailing 12 months. However, this ranking shifts over time - use the Risk/Return Score above for a more comprehensive view that combines Sharpe, Sortino, and other measures used by quantitative funds.