diff --git a/prober/grpc.go b/prober/grpc.go
index e7a5921e..9e4863b0 100644
--- a/prober/grpc.go
+++ b/prober/grpc.go
@@ -111,6 +111,14 @@ func ProbeGRPC(ctx context.Context, target string, module config.Module, registr
 			},
 			[]string{"fingerprint_sha256", "subject", "issuer", "subjectalternative"},
 		)
+
+		probeSSLLastKeyBits = prometheus.NewGaugeVec(
+			prometheus.GaugeOpts{
+				Name: "probe_ssl_last_chain_key_bits",
+				Help: "Contains SSL leaf key information and size in bits",
+			},
+			[]string{"type", "fingerprint_sha256"},
+		)
 	)
 
 	for _, lv := range []string{"resolve"} {
@@ -124,6 +132,7 @@ func ProbeGRPC(ctx context.Context, target string, module config.Module, registr
 	registry.MustRegister(probeSSLEarliestCertExpiryGauge)
 	registry.MustRegister(probeTLSVersion)
 	registry.MustRegister(probeSSLLastInformation)
+	registry.MustRegister(probeSSLLastKeyBits)
 
 	if !strings.HasPrefix(target, "http://") && !strings.HasPrefix(target, "https://") {
 		target = "http://" + target
@@ -207,6 +216,8 @@ func ProbeGRPC(ctx context.Context, target string, module config.Module, registr
 			probeSSLEarliestCertExpiryGauge.Set(float64(getEarliestCertExpiry(&tlsInfo.State).Unix()))
 			probeTLSVersion.WithLabelValues(getTLSVersion(&tlsInfo.State)).Set(1)
 			probeSSLLastInformation.WithLabelValues(getFingerprint(&tlsInfo.State), getSubject(&tlsInfo.State), getIssuer(&tlsInfo.State), getDNSNames(&tlsInfo.State)).Set(1)
+			keyType, keySize := getTLSKeyTypeAndSize(&tlsInfo.State)
+			probeSSLLastKeyBits.WithLabelValues(keyType, getTLSKeyFingerprint(&tlsInfo.State)).Set(float64(keySize))
 		} else {
 			isSSLGauge.Set(float64(0))
 		}
diff --git a/prober/http.go b/prober/http.go
index d79e8e1c..a30e8a71 100644
--- a/prober/http.go
+++ b/prober/http.go
@@ -277,6 +277,14 @@ func ProbeHTTP(ctx context.Context, target string, module config.Module, registr
 			[]string{"fingerprint_sha256", "subject", "issuer", "subjectalternative"},
 		)
 
+		probeSSLLastKeyBits = prometheus.NewGaugeVec(
+			prometheus.GaugeOpts{
+				Name: "probe_ssl_last_chain_key_bits",
+				Help: "Contains SSL leaf key information and size in bits",
+			},
+			[]string{"type", "fingerprint_sha256"},
+		)
+
 		probeTLSVersion = prometheus.NewGaugeVec(
 			probeTLSInfoGaugeOpts,
 			[]string{"version"},
@@ -643,12 +651,14 @@ func ProbeHTTP(ctx context.Context, target string, module config.Module, registr
 
 	if resp.TLS != nil {
 		isSSLGauge.Set(float64(1))
-		registry.MustRegister(probeSSLEarliestCertExpiryGauge, probeTLSVersion, probeTLSCipher, probeSSLLastChainExpiryTimestampSeconds, probeSSLLastInformation)
+		registry.MustRegister(probeSSLEarliestCertExpiryGauge, probeTLSVersion, probeTLSCipher, probeSSLLastChainExpiryTimestampSeconds, probeSSLLastInformation, probeSSLLastKeyBits)
 		probeSSLEarliestCertExpiryGauge.Set(float64(getEarliestCertExpiry(resp.TLS).Unix()))
 		probeTLSVersion.WithLabelValues(getTLSVersion(resp.TLS)).Set(1)
 		probeTLSCipher.WithLabelValues(getTLSCipher(resp.TLS)).Set(1)
 		probeSSLLastChainExpiryTimestampSeconds.Set(float64(getLastChainExpiry(resp.TLS).Unix()))
 		probeSSLLastInformation.WithLabelValues(getFingerprint(resp.TLS), getSubject(resp.TLS), getIssuer(resp.TLS), getDNSNames(resp.TLS)).Set(1)
+		keyType, keySize := getTLSKeyTypeAndSize(resp.TLS)
+		probeSSLLastKeyBits.WithLabelValues(keyType, getTLSKeyFingerprint(resp.TLS)).Set(float64(keySize))
 		if httpConfig.FailIfSSL {
 			level.Error(logger).Log("msg", "Final request was over SSL")
 			success = false
diff --git a/prober/tcp.go b/prober/tcp.go
index de960db2..51b337e5 100644
--- a/prober/tcp.go
+++ b/prober/tcp.go
@@ -98,6 +98,15 @@ func ProbeTCP(ctx context.Context, target string, module config.Module, registry
 		},
 		[]string{"fingerprint_sha256", "subject", "issuer", "subjectalternative"},
 	)
+	
+	probeSSLLastKeyBits := prometheus.NewGaugeVec(
+		prometheus.GaugeOpts{
+			Name: "probe_ssl_last_chain_key_bits",
+			Help: "Contains SSL leaf certificate information",
+		},
+		[]string{"type", "fingerprint_sha256"},
+	)
+
 	probeTLSVersion := prometheus.NewGaugeVec(
 		probeTLSInfoGaugeOpts,
 		[]string{"version"},
@@ -126,11 +135,13 @@ func ProbeTCP(ctx context.Context, target string, module config.Module, registry
 	}
 	if module.TCP.TLS {
 		state := conn.(*tls.Conn).ConnectionState()
-		registry.MustRegister(probeSSLEarliestCertExpiry, probeTLSVersion, probeSSLLastChainExpiryTimestampSeconds, probeSSLLastInformation)
+		registry.MustRegister(probeSSLEarliestCertExpiry, probeTLSVersion, probeSSLLastChainExpiryTimestampSeconds, probeSSLLastInformation, probeSSLLastKeyBits)
 		probeSSLEarliestCertExpiry.Set(float64(getEarliestCertExpiry(&state).Unix()))
 		probeTLSVersion.WithLabelValues(getTLSVersion(&state)).Set(1)
 		probeSSLLastChainExpiryTimestampSeconds.Set(float64(getLastChainExpiry(&state).Unix()))
 		probeSSLLastInformation.WithLabelValues(getFingerprint(&state), getSubject(&state), getIssuer(&state), getDNSNames(&state)).Set(1)
+		keyType, keySize := getTLSKeyTypeAndSize(&state)
+		probeSSLLastKeyBits.WithLabelValues(keyType, getTLSKeyFingerprint(&state)).Set(float64(keySize))
 	}
 	scanner := bufio.NewScanner(conn)
 	for i, qr := range module.TCP.QueryResponse {
@@ -192,11 +203,13 @@ func ProbeTCP(ctx context.Context, target string, module config.Module, registry
 
 			// Get certificate expiry.
 			state := tlsConn.ConnectionState()
-			registry.MustRegister(probeSSLEarliestCertExpiry, probeTLSVersion, probeSSLLastChainExpiryTimestampSeconds, probeSSLLastInformation)
+			registry.MustRegister(probeSSLEarliestCertExpiry, probeTLSVersion, probeSSLLastChainExpiryTimestampSeconds, probeSSLLastInformation, probeSSLLastKeyBits)
 			probeSSLEarliestCertExpiry.Set(float64(getEarliestCertExpiry(&state).Unix()))
 			probeTLSVersion.WithLabelValues(getTLSVersion(&state)).Set(1)
 			probeSSLLastChainExpiryTimestampSeconds.Set(float64(getLastChainExpiry(&state).Unix()))
 			probeSSLLastInformation.WithLabelValues(getFingerprint(&state), getSubject(&state), getIssuer(&state), getDNSNames(&state)).Set(1)
+			keyType, keySize := getTLSKeyTypeAndSize(&state)
+			probeSSLLastKeyBits.WithLabelValues(keyType, getTLSKeyFingerprint(&state)).Set(float64(keySize))
 		}
 	}
 	return true
diff --git a/prober/tls.go b/prober/tls.go
index 3da17a05..b99d998c 100644
--- a/prober/tls.go
+++ b/prober/tls.go
@@ -16,6 +16,8 @@ package prober
 import (
 	"crypto/sha256"
 	"crypto/tls"
+	"crypto/rsa"
+	"crypto/ecdsa"
 	"encoding/hex"
 	"strings"
 	"time"
@@ -87,3 +89,20 @@ func getTLSVersion(state *tls.ConnectionState) string {
 func getTLSCipher(state *tls.ConnectionState) string {
 	return tls.CipherSuiteName(state.CipherSuite)
 }
+
+func getTLSKeyTypeAndSize(state *tls.ConnectionState) (string, int) {
+	cert := state.PeerCertificates[0]
+		if key, ok := cert.PublicKey.(*ecdsa.PublicKey); ok {
+			return "ec", key.Curve.Params().BitSize
+		}
+		if key, ok := cert.PublicKey.(*rsa.PublicKey); ok {
+			return "rsa", key.N.BitLen()
+		}
+	return "", 0
+}
+
+func getTLSKeyFingerprint(state *tls.ConnectionState) string {
+	cert := state.PeerCertificates[0]
+	fingerprint := sha256.Sum256(cert.RawSubjectPublicKeyInfo)
+	return hex.EncodeToString(fingerprint[:])
+}
\ No newline at end of file